What was found
DURING RE-ASSEMBLY OF THE ENGINE, IT WAS FOUND THAT THE FUEL LINE FROM FCU TO THE CHECK VALVE WAS CONTACTING ANOTHER LINE. NORMALLY, THIS INDICATES IT IS INSTALLED BACKWARDS, BUT IN THIS CASE, IT HIT BOTH WAYS. NO PART NUMBER WAS FOUND ON THE TUBE, AND A NEW TUBE RECTIFIED THE PROBLEM. SUSPECT IT HAD BEEN A 'FIELD FIX' SOME TIME PAST.