Though it doesn't seem like much, it should be noted that just a few decibels make a big difference. The Pypes system is 4-8 decibels quieter (from inside the car) than our old system with dumps; since we traded our old H-pipe for an X-style midpipe, we picked up some torque, too-the best of both worlds. Now that's music to my ears.
As you can see in the chart, horsepower was up by 4 at 4,500 rpm, though peak remained the same. Torque, however was up by 5 lb-ft at peak.