Did you use the same dyno both times? I see you live in the bay area, you should have come to the dyno day we had last weekend.
Is it a Mustang dyno or Dynojet?
D'oh, I see the problem, I just looked at the dyno again, and they lost the tach signal above 6500RPM. This happened to a car at the dyno day, they couldn't get a good tach signal, so his horsepower when displayed by RPM was way off, but when they set it over speed, it was much more accurate. The choppiness in the lines is the tach signal to the dynamometer breaking up. As you can see, the curves are heading up, the horsepower curve is on track for well over 150, and then the lines start breaking up. I would recommend going back and asking for a refund or re-dyno.
Is it a Mustang dyno or Dynojet?
D'oh, I see the problem, I just looked at the dyno again, and they lost the tach signal above 6500RPM. This happened to a car at the dyno day, they couldn't get a good tach signal, so his horsepower when displayed by RPM was way off, but when they set it over speed, it was much more accurate. The choppiness in the lines is the tach signal to the dynamometer breaking up. As you can see, the curves are heading up, the horsepower curve is on track for well over 150, and then the lines start breaking up. I would recommend going back and asking for a refund or re-dyno.