I have a 2003 4.4 on a gas conversion which has an annoying miss when going up hills mostly ,which causes engine management light to come on and gives a code P1300 and multiple misfire.You only really notice it on gas not petrol,I have changed the plugs and its still there .I had the gas checked and that seemed to be ok .Is there anyway I can check the coil packs ? as the rubber boots look a bit cracked and old as the mileage is 113000.Any ideas wuld be appreciated.
cheers guys

My idea would be to take it somewhere that actually understands the gas system - if its worse on gas than petrol then clearly the gas system is not mimicking the petrol system accurately.