fuel in oil

I HAVE AN 07 F250 LARIAT WITH 512,000 MILES. I DRIVE HOTSHOT. OVER TIME, I HAVE REPLACED MOST INJECTORS, HEAD GASKETS, NEW ARP STUDS(THIS SOLVED THE PUKING PROBLEM),NEW TURBO, HPOP, OIL COOLER, EGR COOLER, 2 FAN CLUTCHES, 2 WATER PUMPS,ETC. CHANGED MY OIL ABOUT 4 MONTHS AGO AND GOT "20 QTS" OUT OF THE PAN...TOOK IT IN TO MY MECHANIC...COULD BE A HEAD PROBLEM SO HAD THE HEADS REMOVED, PRESSURE TESTED, NEW INJECTOR SLEEVES, ARP STUDS, GASKETS, AND REPLACED 3 WEAK INJECTORS...PUT IT BACK TOGETHER..RAN LIKE A NEW ONE...PLENTY OF POWER, 19 MPG @2000RPM'S...4000 MILES LATER STARTED TO IDLE A LITTLE ROUGH..MECHANIC SAYS LEAKING INJECTOR...PUT IN 2 NEW FD INJECTORS ON DRIVERS SIDE....#2,#4,#6,#8 ALL NEW....4500 MILES LATER...STARTING TO IDLE A LITTLE ROUGH...TOMMORROW WE ARE REPLACING #3,#5 AND #7 INJECTORS(PROCESS OF ELIMINATION)...IF I STILL GET FUEL IN THE OIL AFTER ALL OF THIS....WHAT COULD IT BE? ANYBODY HAD THIS PROB.