Hey guys i have searched for my issue i am having on the forums to no avail.
The problem i am having currently is the car will start no problems on fuel but will not idle and to put it into gear it stalls and/or backfires and stutters a lot it is undrivable on petrol on LPG it has no problems what so ever.

I am hoping it is not injectors but any input would be greatly appreciated i am on a nonexistent budget at the moment. If i have posted a question that has already been answered can a moderator please delete my post, thank you.

Have you tried resetting the ECU First? (Disconnect battery, Headlights on for 30+ mins)

Might be (if your lucky) that the ECU has been trained by the LPG System to run very lean.

If your not lucky, then its the injectors. Thank god theyre easy to get to on an I6. I just replaced my 5.0 ones.

Thanks for the reply, when i get her back i will have to test that but i may have found the issue. It seems that it has a few rather nasty cracks in the head from the water jacket to the valve seats on 2 cylinders. I think the car dealer had used some chemiweld or something similar to dodgy it up for sale i did pick it up rather cheap, only paid $1200.

My solution to the problem was to go to the local engineers shop and pick up a Tickford head fully reconditioned with a new set of head bolts and a metal head gasket.

Just waiting to pick it up from the mechanic now i would do it myself but i like having warranty on these sorts of things.