Originally Posted by shiv@vishnu
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.
I think the 135i catback gets a bad rap. Here is a dyno test a few weeks ago through the stock midcats/135i catback. Not even a golf-tee mod.
91 octane + M10.