Euro headers are a direct swap with the highly restrictive US header/cat version. The next piece, catalytic converters/silencers, are also different between the US and Euro versions although look identical. Swapping all should yield 11 HP and 17 lbs/ft torque (crank) and smooth out the power curves. Anyone venture to guess what the header alone would yield? And can it be fitted to the US catalytic section? I'm trying to decide on a first mod...lightweight flywheel/clutch vs. Euro headers. Cost is close to the same. $1200 vs. $1700 plus installation. From there, next mod is a 3.91 final drive. Options are Dinan or ACS.
Turner Motorsports says... The parts will bolt up just fine. The problem you will run into is with the computer. Normally, there would be a software upgrade to ignore the rear O2 sensors. Such software does not exist yet for this car. To keep the check engine light off you would need to extend the rear O2 sensors back to behind the secondary cats. You will need to add the O2 sensor bungs so the sensors will screw in. This should keep the check engine light off. The correct software would be a much smoother upgrade but it's just not available yet. I haven't seen dyno numbers or even talked to someone who has done the Euro headers so I can't comment on power gains or flow. Using the E46 M3 as an example, the Euro headers and the Euro cats gains 10-12hp. I did talk to someone who hollowed out his stock headers/cats and he said he felt a big improvement.
