hello fella`s although i dont run my lexus on lpg i do run my rangerover 4.6hse on it with no problems at all , a couple of things that may be useful to lexus owners however , when i first bought my rangerover it was running on a single point system this type of system is a bit dated technology wise , especially for the hi tech management systems on modern cars today .
my previous rangerover was a 1994 lse model and that ran fantastic on a single point system , my latest one is a 1998 p38a model and, whilst it ran on lpg it was nowhere near as nice to drive as it was on petrol so, i upgraded the system to a sequential ( multipoint system ) and the difference is incredible both from an economy point of veiw as well as performance.
although have been a hgv mechanic for almost 40yrs fitting the lpg kit is , in my opinion quite a simple diy operation , as long as it is done in a tidy and competent manner , i dont and never have used flash lube and never had any trouble as far as reliability is concerned bearing in mind the rover/ buick v8 is not a patch on the refined lexus v8.
the down side of a single point system is that the mixer acts as a restricter in the induction manifold thus slightly reducing performance , the multipoint system does not use a mixer the gas is ecu controlled thus no or very little noticable power loss , the rangerovers i have owned run even better on lpg than they do on petrol , from an economy point of veiw they cant be beaten they have saved me a fortune !.
as for reliability with the exception of the ill matched singlepoint system that used to be fitted to my latest rangerover i have found them totally reliable and no trouble whatsoever , i bought my kit from a company called tinley tech down in cambridge who , i cant praise highly enough , they were great and offered loads of advice .
i knpw that the rangerover and the ls 400/430 are 2 completly different animals but, they are similar in the fact that they are both powerfull v8 vehicles so the basics of both are similar as regards running them on lpg i hope this may help someone out there who is trying to decide whether or not to run thier car on lpg , finally i have to say that for the bit extra it costs i would definately choose the multipoint system for a lexus , if you have experianced both you would agree i am sure.
rick