I have asked this question to other ctd owners and have been told by all but one that the exhaust length would neither hurt nor significantly help performance. One person told me, and he is a mechanic at DC dealer (Diesel), that the 24 valve required the back pressure of the resonator and muffler. I have since then concluded by reading on here that he was not correct! I have straight pipe on my 2001 ETH and it runs fine. IMO it is not a problem! Anyone else, hear anything different?