My apologies if this has been asked/mentioned but I didn't see it while searching the thread.
Have you done a compression test.. the symptoms you're experiencing sound very similar to a oil contaminated cylinder. Are all your plugs equally fouling? When my car was getting blow by my afr's would be doing exactly what you're describing.. oil was getting past the rings and mucking it up..
EDIT: I searched compression, but I see now you've had a leakdown done. So disregard.
Last edited by MarcusLSB; 07-09-2012 at 10:37 PM.