Did it fall off significantly after peak power? I would not get to hung up on the NA power numbers honestly. I assume it has a "nitrous" friendly grind on the camshaft. Could just be the exhaust timing event is creating some reversion in the intake running NA. But honestly I am not sure if it has a dedicated nitrous grind in it that I would get to concerned about those NA numbers.

I have experienced this more than once and in fact my Predator I currently run did the same thing on the dyno. In fact reversion was so bad it was pushing out the plenum top on the dyno when we ran it and it peaked really low at 7100rpm, for what it is. We knew the cam was not optimal for sure but were surprised at the issues, still made good power just was very unhappy above peak. A cam change/regrind to a bit more NA friendly piece netted me 37 average HP but only 14 peak at 400 more RPM. I still think the cam is holding my junk back but will address it at the freshen up to something more well suited for my deal.