I have an 08 GT with the MRT H pipe. Many people buy an X for a very light HP improvement. I picked the H because it sounds a lot better to me. MRT makes a really quality product. It is also 304 full stainless unlike others with 409 iron mixed in and eventually rust out.
Whipple S/C 550 HO kit, FRPP 3.73 Gears, FRPP springs, Steeda Spyder 20x9 and 20x11, BMR LCAs, BMR ReLo Brackets, Front and Rear CShelby Sway bars, Hurst Billet Shifter, Custom Dyno Tune, MRT O/R H pipe, Borla Stingers