Hi.
I think your problem is fuel supply, not electrics. Could be a problem with the injectors or as was in my case the engine was being overfuelled by a faulty ecu, so it was effectively running on choke all the time which felt like it was missing but ran fine on LPG. Thing to do is find friendly garage and swap ecu with known good one to see if it fixs the fault and if not, isolate which cylinders are misfiring and then get the injectors checked out. The fuel system is pressurised so make sure you depressurise it before disconnecting fuel lines.
Cheers, Nick.