This is my car!
Some of your comments do make me laugh!
I bought the car with the lpg system already fitted so I haven't had to recoup any of the install costs. The guy I bought it off sold it within 10k miles of having it fitted, I have no idea why but he certainly didn't get his money's worth! His loss is my gain, I know he px'd it for a new range Rover Vogue so maybe he won the lottery or something.
I did a lot of research before I bought the car and spoke to the company that did the install, they are one of the best lpg installers in the country which put my mind at rest. Proof is in the pudding as I have had 3 years use out of it with not 1 issue.
In terms of performance difference there is none. If anything if it was tuned properly lpg would produce more power as it is 112ron.
Regarding boot space, yes the tank does take up some space in the boot. Never been a problem for me as I can still fit 2 weekend bags or 2 sets of golf clubs the other side of the strut brace. I can also fit my fishing gear in with no issues.
The prins lpg system is top of the range. I would not consider getting any other system. It has a valve saver kit fitted which resolves any worries of valve seats wearing.
Would I pay to have an lpg system fitted myself- no I probably wouldn't as I don't cover enough miles for it to be cost effective. However I would have no hesitation in buying another car with a Prins lpg system. So much so the next car I want to get is a Monaro with a prins system already fitted.
I have had 3 years of 350z performance with the running costs of a diesel, I don't really see the downside.
If anyone has any questions about lpg systems in general I am more than happy to offer help and advice.
Cheers,
Mark