can anybody tell me wich flowmaster 40 series muffler is right for my ram 1500 5.9 4x4.....like the specific part number, im having trouble figuring out witch one is right ,i already returned 2 of them ,and now im waiting for the third, part number942542 on the flowmaster website and yeah i already cut my old muffler off......kinda like itthat way sounds pretty tufflol!