model GP080LGNGBE088 with a Vortec engine. We drop an engine in this lift and it has been running fine for a couple of years. All of a sudden it started to backfire at the intake and will blow off the CA125 mixer. Change plugs, distributor, rebuilt fuel cut off valve and regulator and off courser mixer. Still it it. Finally we noticed that there is a hole on the oil filler cap and dipstick top if missing. Replace them and it seem to stop till this week. Backfired on cold start and blew off the CA125... totally lost on where to look