I have a yale glp060zg serial A875B35603C that has a tier 2 spectrum lp fuel system. The engine starts and runs normally, but the operator complains of the engine surging. i found while driving the forklift that when returning to an idle the engine would surge four to five times before idling smoothly. i have had similar issues with later spectrum systems when the trim injector goes bad, but have not had much experience with tier 2. it appears to have a trim valve on the mixer and one on the vaporizer. does anyone know if one of these valves can cause this issue or know of something else common on the tier two spectrum systems that causes engine surging? Thanks in advance.