I know running lean can cause a dieseling effect when shutting off the car, or having too much timing, but Im pretty sure I have neither. My 460 is very fresh and Ill include the essentials to help with your diagnosis. I've checked for vacuum leaks and come up short, all bolts are tight and all lines are hooked up. Im pretty sure she's running rich due to the stinky fouled sooty plugs, gas smelling oil, and having to open the choke to get it to start(gets more air to help combustion, lean out mixture), and you have to blip the gas to "clear her out", and it smells like a lawn mower. The timing was set at 8* and it has dieseled on me and now its set at 11, which is still really low. The exhaust manifolds arent leaking to allow for air to get in. Can being too rich cause run-on? I was pretty sure it wouldnt but I could be wrong.