[dalola]

cdog,
While your problem is in fact most likely octane related, as Ron and Craig stated, if that doesn't solve the problem, you may want to check timing, and also check for voltage "leaks" from accessories such as electric fans, fuel pumps, etc.. If it is the later, the instalation of a diode will usually cure it.
Good luck!
Dave
P.S. I'm sure you're aware of how extremely damaging to an engine this condition is!