Do not shoot the messenger ... I am bringing this to the attention of the members of this forum. I know that there are other "mods" that are available and less expensive and I am not going to argue the pros and cons e.g JB3, JB4 and Dinan.
BMW Stage 1 Performance Power Kit Upgrade
Take your engine to the next level
A powerful engine is all part of ultimate driving pleasure. Boost your engine performance and get more out of your BMW. The BMW Stage 1 Powerkit has been developed by BMW engine specialists, and has been tested and refined in accordance with stringent BMW requirements.
• Kit can be fitted to 135i, 335i, and 335i xDrive vehicles
• Available for N54 (twin-turbo) vehicles produced as of 03/08 and N55 (single turbo) produced from 03/10 onward
• Horsepower increase from 300 to 320
• Torque increase from 300 to 317 ft-lbs (manual transmission)
• Torque increase from 300 to 332 ft-lbs (automatic transmission)
• Retains the original BMW limited warranty
Here are the part numbers (for those who wish to take it further)
STREET USE ONLY ..... SOFTWARE ONLY
11-12-2-219-489 (N55) for models produced as of 03/2010
11-12-2-219-488 (N54) for models produced as of 03/2008
If you are going to take your car "on the track", then you will need "Stage II", which is more expensive and involves BOTH software AND hardware Upgrades.