[richs347]

No one makes a long tube header that is emissions legal. They figure the only people who use long tubes put them on race cars and they won't spend the $1000's of dollars to make an attempt to get them past the EPA. The 02 sensors are also not in the usual spots which makes running a vehicle in closed loop more difficult. The long tubes hang down further below the engine on the later Mustangs. They don't hang as far down on the newer cars though.