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Subaru WRX STI VAStage 1 to Stage 4 tuning guide

The VA was the last WRX STI. In the US, Australia and Europe it has the EJ257, a 2.5 turbocharged boxer four with port injection, rated by Subaru at 305 hp and 290 lb-ft, a 6-speed manual and the driver-controlled centre differential (Subaru). Japan's VAB has the 2.0 EJ20 instead (SBI Motor), so check which engine your car has: the tunes and parts here are for the EJ257.

Years
2015–2021
Engine
2.5 EJ257 turbo boxer four
Gearbox
6-speed manual, all-wheel drive (DCCD)
Stock power (US)
305 hp / 290 lb-ft

Updated

Dark grey Subaru WRX STI VA saloon with dark wheels, parked by a garden

Power by stage

Stock is Subaru's US figure at the engine. Stage 1 is COBB's typical gain at the wheels; Stage 2 to 4 are real builds measured at the wheels on a shop's dyno, so they read lower than engine power. US 93 octane equals 98 RON, the best fuel sold in Israel.

Stock305 hp
Stage 1+10–20 whp Stage 2≈320 whp Stage 3400–420 whp Stage 4650+ whp

Names with an arrow go straight to that part's product page for this car. Names in a dashed outline are other brands that make the part; exact links for them are being added.

1

Stage 1: Software only

+10–20 whp

Software alone adds little to the EJ257. COBB quotes typical Stage 1 gains of 5–15 whp and 20–30 lb-ft at the wheels on 91 octane, and 10–20 whp and 25–40 lb-ft on 93 (COBB). What a tune adds as much as power is control: COBB's maps revise the boost and ignition compensations for intake temperature, air pressure and gear (COBB map notes), and the Accessport lets a shop log the engine before going further.

Stage 1 tunes compared

TuneFuelTypical gainTorque gainNotes
COBB Accessport Stage 191 octane (95 RON)+5–15 whp+20–30 lb-ftOff-the-shelf map, stock car
COBB Accessport Stage 193 octane (98 RON)+10–20 whp+25–40 lb-ftOff-the-shelf map, stock car
COBB Stage 1+ package———Adds COBB's Redline intake to the Stage 1+ map

Parts list

  • Engine tune required COBB Accessport V3EcuTekDelicious Tuning

    The Accessport flashes through the OBD port and stores off-the-shelf or custom maps.

  • Intake optional COBB Redline intakeCOBB SF intakeGrimmSpeedPerrin

    Each COBB map lists the intake it was written for.

Before you buyAsk for logs before and after the tune, and don't run a 93-octane map on 95. Ethanol isn't sold at Israeli filling stations, so read the 93-octane row.
2

Stage 2: Intercooler, downpipe and fuel

≈320 whp

Stage 2 is where the STI starts to move. National Speed tuned a 2019 STI with a front-mount intercooler, a GrimmSpeed downpipe with a high-flow catalyst, an equal-length header, a COBB turbo inlet, Injector Dynamics 1050x injectors and an AEM 340 lph fuel pump to 317.54 whp and 355.51 lb-ft at the wheels on 93 octane (National Speed). For US cars that must keep the stock downpipe, COBB's NexGen Stage 2 adds the intake, inlet and fuel system instead, and its flex-fuel version runs any mix of premium fuel and E85 (FastWRX).

Typical cost: COBB NexGen flex-fuel sensor upgrade $980 (RallySport Direct).List prices, Sept 2026, before shipping, import tax and fitting.

Stage 2 results compared

SetupFuelMeasured powerMeasured torqueHardware
National Speed 2019 STI93 octane (98 RON)317.54 whp355.51 lb-ftFMIC, downpipe, header, inlet, 1050x injectors, fuel pump, custom tune
COBB NexGen Stage 2+ Flex Fuel93 to E85——Intake, inlet, 1050x injectors, fuel pump, rails, regulator, ethanol sensor

Parts list

  • Intercooler recommended Extreme Turbo SystemsGrimmSpeedPerrinCOBB

    The 317 whp car runs a front-mount intercooler.

  • Downpipe optional GrimmSpeedCOBBInvidia

    A catted downpipe; COBB's NexGen route keeps the stock one.

  • Fuel system required COBB NexGen fuel partsInjector DynamicsAEM

    1050x injectors and a 340 lph pump appear in both setups above.

  • Flex-fuel kit optional COBB NexGen flex-fuel upgrade

    Ethanol and fuel-pressure sensors for COBB's flex-fuel maps; $980.

Before you buyA downpipe needs approval at Israeli inspection, and without ethanol, which Israeli filling stations don't sell, the flex-fuel maps run on petrol only. The 317 whp car also has a cylinder 4 cooling kit and an aluminium radiator.
3

Stage 3: Bigger turbo and built short block

400–420 whp

On the EJ257, a bigger turbo usually comes with a built short block. National Speed's 2015 STI with IAG's Stage 2 Tuff short block, a Blouch 1.5XT-R turbo, 1050x injectors, a header and a front-mount intercooler made 416.91 whp and 395.86 lb-ft at the wheels on 93 octane (National Speed). Blouch rates its 1.5XT-R at up to about 480 hp with the right supporting parts and tune (WRX Daily).

Typical cost: Blouch Dominator 1.5XT-R turbo $1,996.50 (WRX Daily).List prices, Sept 2026, before shipping, import tax and fitting.

Turbo builds compared

BuildFuelClaimed or measured powerPriceNotes
IAG Stage 2 Tuff + Blouch 1.5XT-R93 octane (98 RON)416.91 whp—395.86 lb-ft; custom COBB tune
Blouch Dominator 1.5XT-R—up to ≈480 hp$1,996.50Stock-location ball-bearing turbo

Parts list

  • Upgraded turbo required Blouch Dominator 1.5XT-RGarrettTomei

    A stock-location turbo keeps the factory up-pipe and downpipe routing.

  • Built short block required IAG Performance

    Forged pistons and rods; IAG's Stage 2 Tuff is the block in the 417 whp car.

  • Fuel system required Injector DynamicsAEMCOBB

    1050x injectors, a bigger pump and a fuel pressure regulator.

  • Clutch recommended ACTExedy

    Ask the shop whether the stock clutch will hold this torque.

Before you buyBudget for the short block, turbo, fuel system, clutch and a custom tune together. A changed turbo isn't road-legal in Israel without approval.
4

Stage 4: Big turbo, closed-deck block and built heads

650+ whp

The top builds use a closed-deck block, built heads and a big Garrett turbo. National Speed's 2017 STI with IAG's Magnum closed-deck short block, built heads and a Garrett G30-900 went over 650 whp (National Speed). IAG rates its Stage 2.5 closed-deck short block for up to 700 bhp (Subispeed), and Blouch's 3.5XT-R stock-location turbo for up to 580 hp with forged internals and a built fuel system (Subispeed).

Typical cost: Blouch Dominator 3.5XT-R turbo $2,085 (Subispeed).List prices, Sept 2026, before shipping, import tax and fitting.

Big-turbo builds compared

BuildFuelClaimed or measured powerPriceNotes
IAG Magnum block + Garrett G30-900—650+ whp—Closed-deck block, built heads
IAG Stage 2.5 closed-deck short block—rated to 700 bhp—Forged pistons, H-beam rods
Blouch Dominator 3.5XT-R—up to 580 hp$2,085Needs forged internals and a built fuel system

Parts list

  • Closed-deck short block required IAG Stage 2.5 closed-deckIAG Magnum

    Inserts close the deck to stop the cylinders moving at high boost.

  • Big turbo required Blouch 3.5XT-RGarrett G30Extreme Turbo Systems

    Blouch also recommends an external wastegate for full power.

  • Built heads and fuel required IAG PerformanceInjector Dynamics

    Heads, valve springs and a fuel system sized for the target.

Before you buyStage 4 is an engine build, not a bolt-on: choose one shop to build, tune and stand behind the whole package. The biggest figures usually need ethanol or race fuel, which aren't sold at Israeli filling stations.

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Quick answers

How much horsepower does a stock Subaru WRX STI VA have?
305 hp from the factory.
How much hp does a Stage 1 Subaru WRX STI VA make?
Tuners claim +10–20 whp at Stage 1, up from 305 hp stock (Stage 1 options).
How much hp does a Stage 2 Subaru WRX STI VA make?
Tuners claim ≈320 whp with a Stage 2 file and the parts it needs (parts list).
How much hp does a Stage 3 Subaru WRX STI VA make?
Tuners claim 400–420 whp at Stage 3: bigger turbo and built short block (Stage 3 parts).
How much hp does a Stage 4 Subaru WRX STI VA make?
Stage 4 is the top of the ladder for this car: big turbo, closed-deck block and built heads. The biggest builds claim 650+ whp. Check which fuel each figure needs: Israel sells 95 and 98 octane only (Stage 4).

Questions to ask the shop

  1. Is my car an EJ257 STI, or a Japanese VAB with the 2.0 EJ20?
  2. Will you log knock before and after the tune, and is the file written for 98 octane?
  3. At what power do you require a built short block on the EJ257?
  4. Do you fit a cylinder 4 cooling kit and an air-oil separator at this stage?
  5. At what torque do you insist on an uprated clutch?
  6. Does the setup keep a catalyst, so the car passes inspection?

Compare side by side: Subaru WRX STI VA vs VW Golf R Mk7 · Subaru WRX STI VA vs Honda Civic Type R FK8 · Subaru WRX STI VA vs Audi RS3 8V

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