My RV6a has an O-360 with an Ellison Throttle Body instead of a conventional carburator. It runs wonderfully, but just won't STOP running! Pull the mixture and it keeps popping and sputtering. Turn off the mags and it'll diesel as well. Turning off the fuel value takes a minute or more to burn the gas out of the gascolator. I've gotten reasonably good at killing the mags, then advancing the throttle as it spins down to achieve and incombustible mixture, but even that isn't always working anymore. Has anyone else seen this behavior? Any suggestions? Does my throttle body need a rebuilt or is that "just they way they are"? It really bothers me to have the engine popping and sputtering and even spinning backward on occasion when I'm trying to shut it down. Really hurts the image, not to mention the potential harm to the vacuum pump!