well reset carbs again. runs real good to 4500 rpm then gets a spark ping and falls on face till below 4000 rpm. don't think im getting mileage out of fuel. but haven't went far. my thoughts fuel level. but disassembled 8 carbs and all were set same so.. advance set to aggressive but ran 8000 miles no problem with revs. vac leak sprayed oil around boots and carbs no difference. I think ive done every thing I can think of going to lower advance see what happens.