70 hp runs great until full throttle. It will throttle up for about 5 minutes then throttles up and down like it is getting spurts of gas. I have had it in the shop a couple of times and they replaced connectors on the power pack and the pump that primes the carbs for starting. It will run full throttle when it is on the muffs but not when it is under load. The gas tanks are new along with the fuel line and bulb. Any idea would be appeciated.