can i buy an 80 series flowmaster mufler to add into an existing stock exhaust system? Will it fit???

yeah it should..if you just mean use the pipe, then yeah it should fit..and if it dosnt, any exaust place can make it fit..but if your going for flowmaster..i'd seriouslly upgrade the pipes, at least from the catback, it's not that expensive...i just hope you mean your replacing the muffler you have now, and not adding a second one, cause i've seen some import kids as a can exaust, to their alreay exsiting muffler...kinda defets the purpous

really, all the muffler is doing is making sound better, and you might pick up marginal power... Save up and get a full cat back, and if you can, headers would be great too. Its one of the best mods you can do to a third gen.

Yeah I aggree, the sound is good, the sound and power gain is awesome, if you get headers, and header back exaust.., If you get a place that wont make you have the cat...you'll be a happy camper..i bought a muffler, and a local place called solo, put new cat back pipe, installed new muffler mounts, and fixed my tail pipes, and installed everything for 50 bucks...thats real hard to beat..