Hey Dave, that 400 was on the Dynojet chassis dyno. It measures and calculates differently. I won't get into it on this thread but, the Mustang dyno will give you real true to the street numbers than the Dynojet. What I've heard is, if you want bragging rights go to them, if you want street and track proven results, go with the mustang.
I think your mind,........is foggy Dave !