Hey, im new to this forum just having some trouble.

i got an LPG conversion on my VZ a few months ago, ever since then been back to mechanics none stop.
> I get message "check powertrain" occasionally - so i got new sensors
> Whenever i switch from LPG it runs smooth and no problems
> After, i switch back to Petrol and i get problems. Engine doesn't start, severe shaking of car
> Ive gone back to mechanics and he's checked computer/ adjusted it - it seems to work fine after but after another 1-2 switches, same problems occur.
> Tried switching from LPG to petrol while car is off, and while its on 100km/h - still problems
> I changed (sorry don't know what its called) the electrical part that regulates air and petrol intake into engine, still problems

am i doing something wrong? need advice, thanks