Saw an article in some HPI or Zoom mag. I only briefly read it though and can't remember exactly what it said.
But the gist of it went:
There's a workshop in Queensland that's actually developing a proper LPG system.
The owner of the shop has converted his BA xr6 turbo to run on petrol and LPG but with proper injection and engine management (different to the normal, "lets blow lpg down the f**king intake pipe and take a brand new engine and make it run like it was designed in the 60's").
After tuning the car apparently makes more torque down low, and switches to petrol seemlessly up high in the rev range to give better top end, or something.