If it like a bolt on the exhaust after the cat, you can also drill it out. That is what I had to do on one of them. Heat burnt all the rust, used lots of deep creep, hit it with a heavy hammer...and nothing. After about 2 hours of trying to get it out i just used a small drill bit and drilled threw the bolt. Then I just used bigger and bigger bits to get to the right size. And I thought the rear torx bits on the calipers were T-50's. And yes, vise grips do work on those caliper bolts---just get someone with long arms so they can leavrage on it.
