Hello, i have just bought a new exhaust system, and i was going to install it today, but when i tried to get the bolts off that attach to the cat converter, they seemed to be rusted on, and virtually stuck. Does anyone know an easy way to remove them?

 

If they are not rounded or rusted to the point a wrench will not grab,
soak with PB Blaster and let it sit for a while. use a 6 point socket or wrench for max contact and give it a try. If no go you need heat, propane torch.
Get it hot, quench with PB. repeat.
Work it with the 6 pioint to try to get it moving.
I all this fails , cut off wheel and new hardware.