Originally Posted by mwahlert
how have you found the factory 335i exhaust to flow once the secondary cats have been removed and catless downpipes have been installed?
Reasonably well it seems. I haven't done any controlled testing of it though. The only reason I know how bad the 135 single exhaust system is was from back in the day when we tuned our first one. Up top, It was 20-30whp down from all the 135s we tested with the same mods/tune. Made sense once I looked under the car.