Darrin Tosh as well as a few others have sucessfully run propane for years with no issues. Darrin did eventually eat a head gasket, but the cause of that is not known to me. Propane fumigation is a well accepted scientific technique for causing diesel fuel to burn more completely. In the proper amounts it is neither dangerous, nor adverse. It does tend to cause higher EGT's due to the more complete fuel burn, so liquid vapor intercooling should help considerably. Folks who have played with that and failed, did so mostly because they just used too dang much! The key is a good vapor mist and the right amount at the right time.