Cosmo,
Here's another thought. Have you considered running chambered pipes? One of my buddies worked in a muffler shop for about 4 or 5 years, and he said that the most impressive exhaust setup that he remembered from his days as a muffler monkey was chambered exhaust pipes. They're straight through pipes, no packing, but are divided into chambers every foot or 18" and do a great job of canceling out harshness and reduce noise volume too, but flow really well. I've seen chambered pipe available for DIY exhaust systems in the Summit Racing catalog, so you might give Summit a call and see if they have anything you can use. Their toll free # is (800) 230-3030.
