Our VZ SV6 runs on LPG - same story here. Holden doesn't do it and claims that it can't/shouldn't be done but there are no issues with running an Alloytec 175/180 or 190/195 on LPG. You need a SVI (Sequential Vapour Injection) setup (there are no alternatives because of the way the intake manifold is designed) and APA already have gas tanks suitable for the VE. SVI costs around $4500 to install. Performance and smoothness will be equal to petrol and economy won't be too far off either (depending on ability of your installer to find the correct tune). You will need a Flash Lube dripper kit to protect the valve seats though. Well worth the investment. The SV6 gets around 550km on 70-75L of LPG around town.
Regards,
Dave