I have stock manifolds into gutted vortec convertors, into glasspacks, into 20'' long tips. Gutting convertors helped alot with sound but at idle i still have a "whiff" sound instead of a deep rumble its like an air noise. Its hard to describe the sound. Anyway would putting a h pipe in it give it a deeper rumble? i dont want to quiet it at all either because its still not really loud enough IMO.