My pops just bought a Nitro with the above motor on it. It has ran fin up until a coupe weeks ago. It as been sputtering an wanting to die. But when you break t over it runs smoothly. Just when at idle it kinda idles up and own over and over but never dies. So pops pulled the oat out and put on hose. He took the cowling off and can hear a noise not noticed before. It was coming from the air compressor. So he put new plugs in and after it running for like 15 mins he took them out. He said the plugs were really black. Any ideas? We thought it might have water in the fuel. Any help would be appreciated.