ON 7/29/19 AT APPROXIMATELY 12:30 PM, WAS TRAVELING BETWEEN 60 - 65 MPH, WEST BOUND ON INTERSTATE 40 AT N.C. MM 31, THE TRUCK LOST POWER (LIMP IN MODE), THE CHECK ENGINE & SERVICE AUTOMATIC THROTTLE CONTROL SYSTEM LIGHTS CAME ON. NOTICED A SMALL AMOUNT OF WHITE SMOKE EMITTING FROM THE UNDERSIDE OF THE TRUCK. COASTED OFF OF THE INTERSTATE AND CAME TO REST IN A USED CAR DEALERSHIP'S PARKING LOT. TURNED THE TRUCK OFF AND OPENED THE HOOD WHERE I FOUND AN APPROXIMATELY 8' FLAME PROJECTING FROM UNDER THE PLASTIC MANIFOLD COVER. DOUSED THE FLAME WITH A BOTTLE OF DRINKING WATER AND TOOK THE PLASTIC COVER OFF WHERE I FOUND THE WIRING HARNESS SHEATHING ENGULFED IN FLAMES. EXTINGUISHED THAT WITH AN ABC DRY CHEMICAL EXTINGUISHER. CURRENTLY THE TRUCK IS AT WAYNESVILLE RAM WITH NO UPDATES AS OF YET. HAD THE EGR RECALL COMPLETED ON 6/19/19 AT WAYNESVILLE RAM AND HAD NOTICED DECREASED POWER AND FUEL MILEAGE SINCE BUT THE DECREASES WERE MINOR AND JUST ACCEPTED AS FACT FROM THE RECALL. I AM VERY CONCERNED AT PRESENT AFTER RESEARCHING THIS SITUATION AND CONVERSING WITH OTHERS WHO HAVE EXPERIENCED VERY SIMILAR EVENTS WITH THE SAME MOTOR.