Onan P220G, Nikki 146 0479 Carb?

Engine has 1265 Hrs, it burns no oil very solid. It runs at 2800-3000 RPM's but at full throttle it will stop frquently. Vacuum gauage drops to 2-3 inches while nowing. With aircleaner removed fuel sprays from the carb when throtrle is increased rapidly. Removed exhaust manifold noticed carbon deposits in cavity around the valve.