ERCUZ what's your location?

Depending where you had the original LPG conversion done, the timing is altered for the LPG rate of burning. Done by the infamous R16 resistor.

Have you changed your injectors and injector seals and guides. LPG is not kind to these things.

I filled up yesterday. 22mpg out of my M103 city driving. Regularly get 30mpg country driving. (Imperial gallons)