Upgrade stages from 370 to 390 Hp for the 3.0T engine found in BMW 135i. 

Stage 1 & Stage 2 upgrades, are presented below.

Stock engine specs:    

Capacity: 2979cc                           
bore x stroke: 84 x 89.6 (mm)
Compression ratio: 10.2:1
Turbocharger: TD03

Power: 306 & 326hp
Torque: 400 & 450Nm

Stage 1: 

Engine upgrades:

-Stage 1 Software upgrade

Engine performance:

Power: 370hp
Torque: 500Nm

Stage 2:

Engine upgrades:

-Full 76mm exhaust 
-Air filter
-Stage 2 Software upgrade

Engine performance:

Power: 390hp
Torque: 520Nm

Software upgrades:

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

Use of 95/100 octane fuel is mandatory.