My 4.9 is run through a Y pipe similar to the Fiero's.
It goes into a 2.5" pipe that's adapted to 3" high flow cat, in the stock location, into another 2.5" pipe that feeds a glasspack in the stock location, and out to a C6 resonated dual tip on the left side.
It sounds really good, but I think it's still too f'n loud. (Or maybe I'm just too old.) It drones in the cabin at freeway speeds.
No way I would run it without a muffler.
88 Formula IMSA Fastback. 4.9, NVG T550
Praise the Lowered!