x and h pipes

Im lucky enough to have before and after numbers that also support the articles Ive read.Both H and X pipes are good and are big improvements over std duals,an H-pipe will have more low end torque in the lower rpm range compared to an x-pipe,but after that the x-pipe takes over on tq and h.p..The X pipe gives you more overall power throughout the range,I have personally seen a car pick up 1 1/2 tenths going from a H to X with no other changes to the exhaust,running mid 11s and shifting at 6,700and as abody said the carb needed rejetting.I wouldnt even run std dual pipes on a performance car after seeing/feeling the inprovement of an H or an X pipe,for me though I will run an X when ever possible.