What size socket are you using? If there is still some substance to the nut, i used 9/16 socket instead of metrics. A 14mm would fit 2 of the 3 nuts, but would not go on the 3rd one for some odd reason. 15mm felt to big, so i tried the 9/16 six point socket and used a breaker bar and about a foot of extensions and they popped right off using some lubrication as well. Try to use a 1/2" drive, although i was limited on tools and broke them loose using a 3/8ths. Just make sure the socket's on there perfect before you start torquing.
If you're past the point of using sockets (completely rounded off), you can back the stud out, not fun, using the star diagram on the end of the stud, although take in mind, i'm pretty sure it is not a torx pattern. Do a search on here and you can read up on it more.
Good luck, it took one guy like an entire memorial day weekend to get his off.
Sorry to hear that Bryant.
I hope you find something here.
I had seen such horror stories about taking these off, I got a (good) muffler shop to replace mine. Took less than 30 minutes - well worth the $40, too.
I recommend that route to others.
I know this doesn't help you now, unless you can get the car to a good shop.