The only thing I can think of is that, at least on V6 car and probably GT's too, the automatic cars have an extra breather tube that connects to the inlet and maybe the sound tube is routed differently on them because of that.

Still shouldn't make any difference when adapting this to a V6 car.

 

UPDATE: Do as ltngdrvr mentions in his post by installing the 90 degree elbow in the "muffler" area of the air cleaner box instead of the tube (from air cleaner box to throttle body). I drilled and screwed in the elbow on the tube part, and the sound tube was about 5 inches too long; to get it to work, I would have needed to route it with several bends to take up the slack to the valve at the drivers fender. By putting the elbow in the "muffler" area, the sound tube routes better to the valve.