So I picked up a extra head for my 1990 CBR600 for cheep because it has a broken exhaust stud. I'm going to replace it and was wondering if there pressed in or threaded in?

 

They are threaded. There is a nice thread on how to repair a broken stud around here too.

 

Spin 2 nuts with a lock-washer between them, then just back it out.
Be sure to soak it with break-free for at least 30 minutes before hand.
If it still won't back out easily, consider applying a little heat from a propane torch.

Ern

 

Had to use some vice grips on it. (wasn't enough left to get a nut on) but it came out!