If I had to guess I'd say you have a dead cylinder on the right side of the engine. For gas to get into the exhaust it must travel up into the exhaust valve. Otherwise it would travel south into the oil pan.
Either you are running so rich that lots of raw gas is not burnt while the engine is running (this is very possible, but you'd see the issue in both pipes) or you have a miss that you are having trouble finding.
Last edited by Midget Farmer; 09/19/2009 8:39 PM.
