Remove and clean the throttle body and flame trap fitting. There's a small vacuum hose tube on the flame trap that gets plugged w/ carbonlike material and needs to be drilled out. If the gasket isn't broken you may not need a new one. Check for any poor vacuum hose connections. May be an air mass meter problem?? Check the connection. Some cables are really tight. Motor movement can pull on the plug and cause problems if your mounts are bad.