I know it's not strictly related, but I had a range rover 4.0 V8 converted to LPG a few years ago, I can say on that there was no power loss, it makes no difference to servicing, and I dont think theres any maintainance as such involved with LPG, according to the firm I used the power loss issues that you hear of is down to the timing becase LPG really needs a slightly different timing setting to petrol and as the system starts on petrol then switches over to LPG they tend to put set the timing somewhere in the middle, mine had a module fitted so it had two timing settings so it was right for both fuels so no power loss that way.