[johnsonj]

Originally Posted by M Baldwin

Try letting some penatrating oil soak on them for a while. But get ready to break some. Get some good quality drills, just in case. If I've learned anything over the years, it's that you should only buy American made drills, or European. That goes for most cutting tools. Anything else is a gamble. I've been screwed too many times by not having good cutting tools. Basically, buy them from a place like McMaster and NOT home Depot. Sometimes the cheapos work, but when they don't, you'll be pissed. You're better off spending a little more.
The way exhaust hardware is heat cycled and exposed to air means that they often rust together. Adding some high temp anti seize at reassembly will help in the future if you ever need to break them back apart.

Fortunately I was able to remove my stock exhaust without breaking any studs.

I kept soaking them in Kroil, using a needle oiler while I replaced my plugs.