Ha,
I think you would need to put me down as a number '2'
It does have two tanks. It's great seeing the range computer not move after 100 miles of motorway driving.
Basically the car starts on unleaded and once warm switches over to LPG. It can be manually switched off if required.
I generally have around 1/4 tank of unleaded and no more!
As for noise, it makes no difference as far as I can tell.