Dually noted Doc and I would say the MB engineers know their product better then we do so that is why we do not see huge gains over what they already have years in R&D. The best gains are just having cutouts and tune for that and due to the constraints in space maybe we are stuck unless someone wants to cut out the fender wells and cobble up a set of headers with that space.
I for 1 am not willing to cut up the wells just to gain 10 or 15 hp.......but given the engine with the s/c even with the cam specs we should be able to gain some hp and tq by freeing up the exhaust. As Les said removing the cats (all 4) does have advantages in hp. I'll bet it sounds real bad as well ......lol Les?

Of course here in CO we have emissions standards so cannot remove all 4 cats. Always something holding us back.