I'm thinking of using these guys for the LPG conversion on my XJ Orvis. http://www.professautogas.co.uk/
Well, not making any claims about best or not, but picked up the GC on Saturday after conversion @ Prins UK. Nice tidy job of work, all the parts neatly and securely located, all pipes & wires routed well, mounting brackets properly made and painted, they even repaired the plastic engine cover that was already cracked when I got the car. I can't really tell the difference when it's on gas or petrol. Only real clue is the fuel gauge isn't moving, and the 'miles to empty' figure has gone up, rather than down. Poor thing is confused! Switches over to gas in less than a mile from cold (does depend on ambient - it's set to switch at 40 degrees water temp). When over that temp, it switches to gas after 5 seconds. Driving along, if I switch back & forth I can't feel or see any change at all, other than the status lights on the wee switch and the faint click from the gas solenoids.Proper job.Also nice they way the guys who did the job took the time to show me round the installation and talk through how it all works, and explained why they did certain thigns in a particular way.The biggest problem I can foresee.....I am a bit less shy of the throttle pedal now.....so I don't think I'll be getting quite so many MPG as I could....but it's still going to be our cheapest car to run.Very happy, heartily recommend Prins Autogas UK in Wolverhampton. Not the cheapest, but I reckon cheapest is often a shortcut to agro.