Thanks Dan and Dutch. I think I'll try the de-carbonizing and doing what Dan said, especially since those hex bolts are on so tight. Since I know nothing of the machine's history, it could be they did something like running 32:1 dino oil. Maybe some Amsoil saber @ 50:1 and a little seafoam will clean things right up.
Is it fairly easy to get rid of the CAT, by modifying th4 muffler or getting a replacement?