Recreational Vehicle Lpg Tank Valve/gauge problems of the 2008 Chevrolet Cobalt

Bought in Nov 2015 from carmax. Immediately had to flush all fluids, replace breaks, and rotors. The car shuts off. Gauges go haywire, all warning lights come on and then the power steering cuts out. The car then shuts down. This series of events happens whenever it wants to. When I've just put gas in it, on the interstate, in an intersection, in the rain, or in 85 degree weather for example. So far GMC has replaced the fuel pump or something to do with the fuel pump (I'm no mechanic, so I don't know exactly what it was) but I was told it was fixed. Obviously it's not. This problem has now happened while the vehicle is in park. I even have video graphic proof. Honestly, I'm terrified of the car and I just want rid of it with my money back. What happens when this car kills me and or other people while I'm driving it? I've set up an apt with carmax to have it looked at, but if they can't recreate the problem what then? I've got an appraiser coming out from chevy on this Friday, October 9th. I just need someone to help me.

I was on my way to work this morning on and noticed my car 'stuttering' as few moments at a time. After I proceeded from a stop position and continued off the highway, the car dashboard began to light up, almost as if it was shortening out. The speedometer, fuel gauge, and my rpm kept moving back and forth quickly. There were multiple messages flashing such as powersteering, low traction, no traction. My check engine light, antitheft light, and the traction light kept flashing. Then I lost power steering and my car ultimately 'died' on the side of the road.