A buddy of mine bought Pace setter headers for his M42 318i. I advised against it because I knew they were shitty from years ago when my friend put it on his Talon TSI. The stock 318 headers are already SS and flow very nicely. He put them on anyways, but hey, they were less than $300 for a custom make. They were 4-1 style made for high end power as compared to the 4-2-1 style made for mid-ranged.
When he got them the welds looked like such an amature job. After they were installed we took a ride in his car and the car was torqueless, even more so than before. It seemed to pull slightly better at 4000RPM but then went kaput again at 5500RPM. There was definitely a loss of torque as expected with the 4-1 style headers. However, the high end didn't feel any better either, infact it felt worse. Anyways, about a month later he dyno'd it. It had 107HP @ 5200RPM, keep in mind rear wheel HP. That's already messed since the peak HP was pushed back to 5200RPM instead of 6000+. There was a significant dip in the power curve after 5200RPM. I didn't have a stock M42 dyno plot to compare with, but our butt dyno's already told us that these headers weren't even worth the metal they were made of.
He had a few mods, intake, chip, exhaust and TB just like my car
However, his HP figures were much lower than even stock numbers with that crappy header.
After that he removed the headers and restored it back to the stock headers, instantly felt better.
We decided to call the company and ask them how they could sell such a shady product to the public. We were surprized as American companies usually make some kick ass headers/exhaust systems. They informed us that they stopped making these headers for BMW's more than 5 years ago because of the number of compliants. So that's that then, they probably just sold my friend some left over stock they had laying around. Anyways, in conclusion, these headers are shit! Don't buy them!
Thanks for your time,