Yes, I got an X pipe with the purchase of my longtube headers from American Racing.
I believe you could also get the H pipe. Ive seen them from other brands like KOOKS, STANLESS WORKS, BBK. Id check the usual exhaust companies. and look at other post.
H pipes don't seem as popular as they used to be. You might want to check out the MAC Prochamber. I ran one on my old 2001 GT for 7 years and LOVED it.
To pick up a few more HP/TQ across the entire RPM range and improve over the crimped POS stock mid-pipe. Exhaust note improvement. The same reasons people have been swapping them out for years.