I had my y2k 4.6 converted to lpg at Medway Dual Fuel. They were very good, and the fitting job was excellent. I had a Prinz fitted which very much wasn't the cheapest on the market, but the car runs substantially better on gas than it does on petrol, smoother and clearly making better power. My only gripe is that Prinz tell you that you'll get 80% of the mpg you get on petrol. I've yet to reach 70% and that's after taking it back a number of times for testing, which even included an on the road calibration test on the M2. My mpg tests were done on actual usage, filled at the same pump, at the same filling station, over thousands of miles, so the failing is in the Priz system. I spoke to Prinz themselves, and if you phone them today, they'll tell you you can expect at least 80% of your petrol mpg. Having said that, the intallation was excellent and I haven't had a peep from it in 26k miles.