Hadn't considered that... had presumed that the turbo took care of the air, and the vaporisers supplied enough gas to keep the injectors meeting the demand
Rustled this up...
http://www.go-lpg.co.uk/Turbo.html
Could the Stag 300+ therefore be suitable
The vapouriser regulates vapour pressure relative to manifold vacuum / pressure so that shouldn't be an issue as long as the vaporiser is capable of providing enough flow. The thing is, the power ratings quoted for vapourisers are optimistic for a naturally aspirated setup, in my opinion. For a turbo setup the vapouriser is called on to deliver the vapour at a much higher pressure and a turbo engine will probably want to run richer at full power anyway, so I'd forget the rating on the vapouriser and got for a pair of KME golds, one per bank.
Not sure I'd trust a Stag on that. Pretty much all our Stag installs have some sort of minor running issue and they only just keep the fuelling within the tolerances required to keep the Omega's engine ECU happy. On a more modern engine with the added complication of forced induction it could get tricky. Then again, I have seen nothing to suggest that any of the "premium" LPG kits are any better.