I HAVE A 91 GMC SIERRA AND MY TRUCK STALL AFTER ABOUT 5 MIN IDILING. AFTER I RESTART, THE TRUCK LOPE FOR A FEW SECONDS AND RETURN TO NORMAL IDILING. BUT SEEM TO BE LOADING UP WITH FUEL CAUSE BLACK SMOKE COMES OUT OF THE TAIL PIPES. I CAN DRIVE IT AND BUT BURN ALOT OF FUEL. I HAVE CHANGE OUT SEVERAL PARTS INCLUDING THE EGR VALVE, MAP SENSOR, IDILE CONTROL VALVE, O2 SENSOR, TEMP SENSOR (THE ONE ON TOP OF ENG.), FUEL FILTER,COMPLETE TUNEUP INCLUDING WIRES AND ALSO A NEW ECM BOX. WHAT ELSE IS LEFT TO CHANGE OUT. PLEASE HELP ME