Originally Posted by jcjmw

Wow, I am a little surprised that the chips or ECU reprogramming for the E55 will not provide a respectable gain in hp. I figured that the ECU modifications would result in some kind of "feel in the pants" hp gain on the E55, especially giving the $$$ that some of the vendors are asking. So, I guess the only modifications (regarding HP gains) that I can do to the E55 is (1) supercharger (which I will get later b/c of the costs); (2) K&N filter (which I already ordered); (3) the pulleys (which I will avoid due to concerns about possible detrimental affects on the engine); and (4) and providing a heat sheat to the air box - as discussed in this forum's topic "CLK and E 55 Performance tip." I would like to upgrade the exhaust. However, nobody has published or provided any reliable info on the gains that I could expect on a E55 from upgrading the exhaust. Am I correct or have I missed something? By the way, thanks for everyone's reply. Your info has been very helpful.