Well that's one helluva situation... Air supply seems okay, fuel supply seems okay, I'm assuming electrical system is okay as codes would most likely pop up, so I wonder a couple of other things, one being water in the gas tank, in which case a bottle of dry gas may do the trick, or I'm wondering if your catalytic converter may be at fault. If the latter, it seems as if codes should have popped up for that, but maybe not.
A further thought, have you checked your spark plugs, and indeed if the spark plug wells are relatively free of oil, they are known to fill up with the stuff through the valve cover gasket, and while generally innocuous, that could pose a problem.