Breaker bars are tough to get on exhaust parts...
Box end wrenches and a dead blow hammer should do the trick. Be prepared to run to lowes to get replacements as if they are really rusted/munged as exhaust bolts get, they will snap the bolt instead of losening it.
The last option are "nut breakers. They basically crack the nut in half by pressing a cold chisel into one og the flat sides. I have a set, or harbor freight has them for under $10 I think.
http://www.harborfreight.com/cpi/cta...emnumber=40929