Running properly on petrol first is my advice. One thing I would suggest is to go and get a decent opinion from a good garage. I know it sounds daft but I feel this problem will be cured by a good diagnosing garage in about 15 mins whereas it could take you days and days. The chaps I occasionally use will put a gas sensor up the exhaust (after checking codes) then systematically unplug sensors. 15 minutes they'll have found the cause.