this is just a thought... but i work at briggston and as the motors come down the line and go into the run tunnel(fire them up and check for defects) if there is something that would call for some type of reject(carb not right,head bolt loose,bad valve, bad muffler) there is like 20 codes thay take and write a code on it that matches the defect so the set up knows what to look for and repair it just a thought as not all cars have the markings