John,
The dynos were both Dynojets. Dyno Brain was right on the money when he said all dynojets read within 1% of each other.
The difference between the two is what goes into the actual hp calculation. I spoke with Brian about it and he clarified that both dynos read the same raw, they both calculate torque very accurately, but when the mustang factors in weight of the car, coefficent of drag, probably some others...that produces the HP differance. There are also a few differant ways of correction and smoothing which people with intent to inflate numbers, could.
Doug,
Buck's dyno at dynotune was off by 400rpm. RPM is a crucial thing in the HP equation. We needed to veriify everything was a clean. At auto asset's they run WinPEP 7, which the RPMs were spot on with Buck's car. On WinPEP 6 however...the dyno reads 6,500 - I saw it with my own eyes while the car was hitting the revlimiter, but actually charts it to the right by 400rpm. The graphs and power are the same, they just are shifted as a whole along the X axis.