I've owned a few gas converted vehicles including a monstrous Discovery with a chip tuned 4.6 V8 ! Never had a moments bother.
My current day van, a 2000 MY Vito is on LPG and is truly superb with no issues over the last year. Its very smooth and quiet with no perceptive loss of power and, if I work it out right, I can fill up at a certain supermarket for 55p a litre !
I've saved a fortune.