Originally Posted by skierman64
My question is if the car comes with headers from the factory, how much a performance increase do you think aftermarket headers will give you? It's not be as much of an increase as going from a manifold system to headers like you did in the E46.
The factory headers for the M3 are essentially equal-length shorties with a catalytic converter welded on just after the collector. The primaries are relatively narrow in diameter, and the tubing is pretty convoluted, so it does sound like there is room for improvement, particularly if it comes either with a high-flow cat or catless.
Note: This is based on my rather unscientific observation from looking at one of these off the vehicle, at the Dinan facility in Morgan Hill, while I was being given a tour of the place.
Steve Dinan said they *might* come out with a header for the car, but that they weren't completely sure they were going to do it.