Just buy a x pipe and go to a shop to weld up 2.5" straight pipes. This is basically that but I have 2 18" resonators in the mid pipes. The 5k rev maxes out my db reader at 130 db from about 4 feet away. I never tested at further distance. In the car with windows up or down under wot the meter reads 113 db. I do have an ART type catless test pipe setup though.
PS, play this through your tv speakers
http://m.youtube.com/watch?v=Gg8xjNUmuII&sns=em