Got an 85 TPI 305. This year had factory 3 in. into & out of cat, 4 bolt flange on cat. Exhaust pipe then tapers down to 2 1/2 in. into stock crossflow muffler, all factory mandrel bent, including tailpipes. I've already "modified" the cat, and the stock muffler sounds surprisingly healthy. Now don't laugh....does anybody know if I REALLY stand to gain that much more performance by going to a Dynomax, or Flowmaster crossflow muffler in place of stock OEM part? I feel I freed up alot of restriction with "modifing " the cat, and the stock muffler does not sound all that restrictive now. What do you think???Thanks in advance.

 

A freer flowing muffler will always have gains over a stock muffler. Do whatever though, if it sounds good and still is good why not wait until it needs to be replaced??

 

I'll take IROCZTWENTYGR8's side a little further and tell you my motto... "Replacement time is upgrade time."