prado stalling

[prado fan]

hi guys
several months ago my prado (1998, converted at 160,000km now on 300,000km) stalled as i was driving, with no warning. restarting it on petrol was very difficult but we managed. it then stalled several times on the way home. it went well for a few drives and then suddenly stalled again ( on petrol i think) it went in for a service. mechanics could find nothing wrong but the service and tune seemed to sort out the problem and all was good for several months. yesterday as i was turning into a road, it stalled again (of course that means that i lose steering - a bit scary). i restarted no worries, but it stalled almost straight away. i then flicked over to petrol and drove the last km home without stalling.
any thoughts on what we need to be looking for?

---------- Post added 06-08-11 at 12:23 ----------

...i forgot to mention, it seems to be going through petrol as its running on gas, or at least burning through petrol really quickly when i switch over