Supercharged Cobra HELP???

[chuckhines]

My buddy has a 1997 Cobra w/ a Vortech Supercharger, 3.73 rearend, custom burned chip, subframe connectors, a B&M shifter, flowmaster duals and an x-pipe. The car is a 5-speed manual. He just got the car back after having the FMU calibrated, his exhaust leak fixed, and a new belt put on the supercharger. This car hadn't been run at the track since the supercharger was installed until yesterday. Before all the above listed mods he said it ran a best of 13.91 on radials at the track. Since the all of the mods, yesterday he ran a best of 13.93 under very good conditions (65 degrees, sunny, low humidity). Traction wasn't a problem at all, he only got a little tire spin off the launch, maybe 10-15 feet. What is the problem here??? The boost gauge showed 4-5psi on the runs. It seems to me this car should have been a lot faster than it was. Any help would be greatly appreciated. He was really upset that he was getting beat everytime by my another friend's 1994 manual z28 with only minor bolt-ons.