How much gas do you have in the tank right now??????????If you could lower the level to near empty you could just add 5 gallons of a higher octane to see if it helps-------BUTTTTTTTTTTthose higher octane fuels do need to have jetting increased--------
do you have any jet numbers and cfm ratings of your carb and manifold???????? what do you have for exhaust? How /where do you use the exhaust guage?????? any leakage in gaskets or collectors?????