Originally Posted by BEAR-AvHistory
Here is what BMW says:
"The BMW Performance exhaust system invigorates engine output by allowing engine by-products to exit the vehicle more efficiently. RPM performance is heightened and engine performance is increased by up to 5hp and 3 ft-lbs"
Key words are UP TO which suggests best case. Since BMW posts all it power numbers at the crank not the wheel the exhaust does not do squat for performance but it does sound good.
Anyone who believes BMW is in error with their numbers should post before & after dyno runs.
I wont say that the PE will give you a big jump in power, but its also important to note that BMW's specs are given for a stock vehicle. If you factor in the removal of the factory cats in the DP's, along with a tune that runs much higher boost (larger volume of exhaust), you can see that anything that will create less backpressure is going to improve power. Given that the PE is basically straight through, i wouldnt be suprised to see a gain of atleast 5 whp on a FBO car. Paired with a midpipe cat delete, maybe 10-15whp. Just speculation though, i have no dyno comparison.