The only time it runs under 350 is when its warming up or you stay under 45 mph. Any attempt to go over 45-50 mph on flat highway in florida and you are 360-390. I have not experimented much above 350 as i was told that is the safe threshold. Next time he is available he will check plugs again and carb jets, mixture.
My new worry was last night driving for 4 miles each way and having the oil pressure gauge pegged when driving and around 60 at stop lights, burnt oil smell. I checked under car when back at shop and didnt see anything going on under the car or anything. Didnt see smoke coming off the engine somewhere but i thought maybe i saw smoke come up on me at one stop sign but didnt see again.