I had the same problem everyone does - seized bolts on the back of the cat. Got them off with some drilling, grinding, pounding, cursing.....
Someone told me they are iron bolts. Are they? Anyways after some research I am going to use Monel 400 bolts as they are supposed to maintain holding strength up to something like 1250 degrees f. And they are supposed to be corrosion resistant as well.
My UR cat-back exhaust arrives tonight! So my question is this:
Am I worried too much about this? Some of my buds are saying I am. Does anyone have any success stories with any other bolt material?

Tried searching and couldn't find anything.

 

Grade 8 bolts work with out a problem.

 

I used Grade 8 and no problem thus far and its being almost a year.

 

Monel is a sick *** material that I think is a little unnecessary for a cat. Just use grade 8. If you have to take it off against just use some PB blaster galore and hold a torch on the bolt until it super hot, it'll make it soft enough to remove.