You know some of us old timers were accustomed to going back to idle for a few seconds before turning off any gas or diesel engine. But the manufacturers do change things. I had a Toro ZTR with a Briggs & Stratton engine, and if you turned that thing off at idle, you'd wonder why the backfire hadn't blown the muffler off. But if you turned the key off at wide open throttle (which is exactly what the manual said to do), it died a nice peaceful death. I'd only use a choke to kill one as a last resort until I could solve the problem properly; not as a routine thing.