[crabman]

Originally Posted by jamminj007

Porting the tri-y will minimal at best. In stock form they flow extremely well. I would wager that even changing just them out for long tube headers would net minimal gains over the factory tri-y. GM did their homework and unless you are doing major mods headers wouldn't be worth the $$$$.

Nah, people are reporting decent gains and when you think about it they cant miss. At most they're going to have a single set of cats located further back which means you have the gains from the long tubes themselves, a more efficient merge, loss of at least one set of cats, those cats are better placed and less restrictive. Or no cats for those frisky folks that are so inclined. If OEMs didn't need to meet light off requirements LTs would be standard on most NA cars. More efficient, lower cost, easier to package. It's all win.