Recently purchased a vl exec dual fuel,and when i switch over to petrol it struggles and eventually dies. Has fuel,pump works. It does run for a while but not well. Once it dies the motor shuts off power steering goes brakes the lot. Was thinking o2 sensor on exhaust system ? But still car runs a bit rough on gas. Has a bit of an exhaust leak at the manifold/engine pipe flange. Would this cause it to cut out/ send the computer a wild reading or something ? Any clues or answers would be greatly appreciated.

fixed,plug leads and 02 sensor were stuffed

thanks, mine has similar prob