The tuning stages vary from 340 to 380 hp for the 2.5T engine of Impreza WRX STI.

Stage 1 & Stage2 upgrades, are presented below.

Stock engine specs:    

Capacity: 2457cc                           
bore x stroke: 99.5 x 79 (mm)
Compression ratio: 8.2:1
Turbocharger: RHF5

Power: 309hp
Torque: 393Nm

Stage 1:

Engine upgrades:

-Stage 1 Software upgrade

Engine performance:

Power :340 Hp
Torque : 470 Nm

Stage 2:

Engine upgrades:

-Free flow air intake
-Full 70mm exhaust including Free flow catalytic converter
-Stage 2 Software upgrade

Engine performance:

Power :380 Hp
Torque : 500 Nm

Software upgrades:

Boost control is achieved using the OEM ECU and N75 valve.

Use of 95/100 octane fuel is mandatory.