Is the exhaust on a 99 Grand Am the same as a 99 Z24 Cavalier? Is the pipeing ran the same? Are the muffler hangers in the same spot?
honestly i dont know if they are, but i realy doubt it, different platform, different design. but with gm's interchangaeability.....who knows.
my suggestion, take a look under a GAM and see if it looks the same.
out of curiosity why do you ask?
so your lookin for quad rear pipes...?
Yes. I like how it goes from over the axle to the "single" muffler and then it comes out both ends of the muffler to make a dual sided quad exhaust.
it would be the same as doing a camaro muffler. it's called a crossflow muffler. I would just buy the muffler and tips that you want then take it to a muffler shop and have them install it.

2009 Ford Mustang V6