After struggling with the dash light turning on and the unit going into limp mode, we changed the following items:
LPG regulator
Carburetor Diaphragm
O2 Sensor
Temperature sensor
Spark plugs, wires, rotor, and dist.cap.
Air filter
And after all this unit was still doing the same, after about ten minutes idling the light on the dash would turn on an no more throttle, unit would drive really slow.
After paying attention timing the light and idle we found out that the little solenoid valve next to the regulator with the vacuum lines would start making noises and the light would turn on.
We decided to unplug the ground wire (white wire) and tested again, unit started working perfectly fine, we left the unit idling for 40 minutes no more light, no more limping.
We test drove unit for about two hours and worked fine.
So getting rid off the solenoid would solve the problem.
I hope this is helpful, too much headaches, so I just wanted to share.