Originally Posted by pmb458
Hey guys, I am new to M3. Does any aftermarket system adds hp or tq? It seems like it's all for sound. How about IPE or akrapovic? Will I loose torque if I open the valves? Can't find any dyno for it.
Any exhaust that removes the primary cats will make power. They all make pretty much the same. Completely catless make about 10hp more than HFCs in the secondary location.
No exhaust that retains all the cats will make significant power.