Hey gang,
Just wanted to update you with some info on the new header for the M3. They will arrive mid-July. As I had initially suspected, they will replace both the stock header AND cat. Why? Well one of the reasons the Euro M3 has a bit more power (other than DIN conversion) is because of the placement of the cats. The 2 pre-cats are actually in the header. On the Euro cars they are further back than on the US cars. Hence because they activate earlier on the US cars, we lose about 7hp. So, the first thing I would guess the SS system does to gain power is place the cats a little further back, a la Euro M3. There are still some questions and unknowns like wiring for the O2 sensors and post-cat placement, etc, but we're looking into that now. I will update you with more info as I find out from Italy.
Also, there is no current ETA on the sport resonator or racing pipe (cat replacement).
For more info, check out our dedicated E46 M3 page on our online catalog:
http://www.evosport.com/product/e46m3/