THERE could be a number of reasons for your problem, Paul, and as you've tried many fixes I'd suggest you go back to basics. Make sure all the settings are correct as per the specifications, then concentrate on the oil side as it seems likely that its oiling the plugs. It seems to do it so quickly that I would expect to see some smoke from the exhaust and some loss of oil as measured on the dip stick. Check the compression to see if there's been any drop, check valve-stem seals for any leakage. It doesn't seem likely that it's a fuel problem since you've switched fuels and still have the problem. Using hotter spark plugs might help, but that's treating the symptoms and not the problem.