Stacey Davids Gearz. H pipe verses X pipe

A friend of mine had an exhaust shop and a 408 stroker 351 Cleveland in a 68 Mustang. He was constantly modifying the exhaust to get optimum power and a certain favorite sound he was chasing. He also was a close friend of a guy who ran a tune up shop with a chassis dyno. He did an apples to apples comparison of various diametrs of H-pipes and a couple of different X-pipes and what he found on his car was almost zero HP difference between them all. The sound quality changed more than power. The last time I saw his car he had an X pipe on it with some Borla mufflers and tailpipes all the way out the back with turndowns. It still wasn't yielding the exact sound he wanted but he claimed that the setup was among the highest power producers he had run. I loved the sound so I put an X pipe and Borlas on my car and it sounds completely different. I still like it really well but I guess Mopars and Ford Clevelands just sound different.........and I have no idea about power as I don't have the luxury of unlimited exhaust parts or chassis dyno.