My boss recently purchased a gp25 with a SOHC 4g63 Mitsubishi LPG engine. The lift ran fine when we got it but was dumping coolant into the oil and oil onto the floor from the head gasket. We pulled the head and sent it out for work and replaced the gasket. Once everything was ready to go the engin ran like crap and sounded very "bogged" down at idle. Hot or cold you can stall it by operating the lift or steering wheel at idle. For us to run it we have to keep it alive with the pedal constantly being feathered but it still doesn't run correctly. The engine acts like the timing is out but I've checked the timing multiple times and I can't get it any better than what it is now. The compression is 150 cold on all cylinders. We have tried a different LP tank too. The plugs are good with a gap of.030 and on my tester I'm getting a nice arch at.25". We disconnected the hydraulic pump and it still runs rough. The engine only starts when the throttle is opened at 50% or more. I have tried running the engine on starting fluid and gasoline and still runs like crap. I have even tried putting very small amounts of starting fluid in the intake while running and if a drop makes it in the engine falls on its face like I'm pouring water into the throttle body. I am at my wits end and can't figure it out. It seems like it's running rich but my knowledge of LPG systems is slim. I've checked the LPG filter and lockout and everything works and seems peachy with that. The system is a impco model 100 mixer, a cobra 101025 regulator, and a cobra model n-vff-30-2 w/p 312 psi fuelock. Any help is appreciated thank you.