Like First Banshee said, check the cable.
When the throttle is stuck wide open, flick the throttle a little bit, usually will come unstuck. Mine has done that when moisture gets on the slides.
I'm in MI as well, mods listed below, 320 mains but pretty sure that i am RICH on the mixture. When I put my PC's on i went up on the pilot jet size.
Let us know what happens.