Anyone know how to get these bolts off I’m trying to put on a cat back exhaust and I think these bolts coming off of the catalytic converter are welded or something, any suggestions?

 

This is why it's important to do research before you start a project. Those look like they were studs. Your only option now probably is to have someone with a torch blow them out then you can replace with bolts.

There might be a minor possibility of just drilling them out once you cut them off flush but even then you'll probably burn through some bits.

 

turns out they were pressed in bolts, they hit out with a hammer just needed sea foam deep creep and they came out

 

Awesome that you were able to get it sorted.