They should be able to calibrate their dyno, the local Studka brand dyno I use to test on found out by calibrating it after a conflict with the former operator it was making more power before calibrating it than after, 975HP at 7300 RPM on a 572 C.I. bracket motor with max ported 440-1 heads and a 440=3x intake and a single 1150 CFM Dominator or what ever size that carbs was.
We calibrated it and it lost right at 100 HP with all the same temps and air density
Dram ( RIP ) was correct on that dyno being happy before recalibrating it
My motor still made more power than his did with the same parts