Hi, I have a 1990 GQ fitted with the RB30 motor. It went ok on petrol but when I had the gas fitted it was shocking gutless. I offered to pay extra to have impco kit fitted but the bloke at JR gas in geelong said they only fitted OMVL to that motor. After 2 years of struggling along I finally spat the dummy and fitted a 300A impco mixer and Model L converter I had laying around from a dead XF falcon. It was like adding 2 cylinders to the motor the Patrol will now run the same on gas as petrol. I threw the OMVL converter as far down the paddock as I could and it can stay there till the scrap man comes again. My problem is that it is hard to start from cold, is this to do with low manifold vacuum or is it likely that my old converter is a bit gummed up? In the days of that black tar constantly gumming up your converters I used to fit a 1/4" ball valve in the top and bottom of the converter so I could soak/flush with petrol when it was hot this way I only ever stripped one converter on the 10 gas cars I have owned. At the moment I can start it on petrol and switch to gas but its a bit of a nuisance, I made the fuel tank and it only holds 40 litres with no gauge. 
Steve
Steve