v8 disco 1 trouble starting when warm

My girlfriends parents disco 1 petrol v8 with lpg conversion starts cold no problem but when warm becomes unreliable and sometimes wont start at all until cold again so was wondering if it had a cold start valve or sensor that could be causing the problem its been on a landrover fault reader and shows nothing and they just paid to have distributor replaced today but no different starts on petrol fine and switches to gas no problem with either distributor only seems to be troublesome after being ran a while wondered if anyone had a better idea what to look for i personly suspect some kind of choke/air intake temp sensor problem but have no experience of a v8 petrol landrover engine any help would be great