volvo 960 auto box

i have a 960 with the switchable autobox it had an lpg kit fitted 4 years ago it has now started to go wrong in the way that the arrow on the dash board has started to flash to say it is in the wrong gear it has also started to flash between all three settings on the switch in the centre console this is sports-economy-winter it also goes into limp mode and will only do 5 mph or i compleatly loose drive ihave been told by various so called experts that it is either the gas conversion that is causing the problem or that the selectable auto box switch or the starter-inhibitor switch are causing the problem and need replacing