My thoughts exactly. Check your plugs, timing and fuel. Remember, running super high octane fuel is not beneficial if the compression is not high enough. In fact it is worse. Run what is recommended. GOod luck and keep us posted.Originally posted by Baja Daze
As many others have said, it definately sounds like run-on or dieseling.
Bad fuel, with a degraded lower octane can cause this; low octane will cause the fuel to light off(detonate) prematurely, often times just the temp of the combustion chamber along with high compression will be enough.
Also, carbon build-ups will leave large enough deposits on occasion, and will glow red hot within a combustion chamber; this can mimick a glow-plug and will continue to light off the fuel after the spark is eliminated.