You want real power increase? B&B exhaust system really added very noticeable power to my E36. I have an older version so I also changed the chip out with an Autothority chip programmed for that new exhaust system. Added the cold air Autothority K&N cone filter on the high flow intake & it really rocks now. One thing, with the new chip, I have no top speed limiter & increased RPM by 600. I now MUST use 91 octane fuel as the knock sensors have been taken off line with the new chip. All well worth it as I would NEVER put regular gas in the car.