If you do a search you should be able to find all the info you need. This topic has been beat to death on this forum and it should be easy to find
the crossover in the catalyst pipe is either shaped like an X or an H. The xpipe has a higher pitched sound with less rumble and the h pipe sounds more like an older muscle car. FYI- On the S197 cars, you aren't gonna get that "old" muscle car sound either way. I have had several setups on my '06 GT and none of them sound as good as my old 5.0 liter. Or maybe I am just too old also
Here's a thread from the 2-valve 4.6 section that may help some. http://forums.stangnet.com/showthread.php?t=607174
Thank you for the info. The info from Black2006gt is what I was after. I also have a 06 gt. I think I will use an H-pipe.