Judging by that, I mean i'm no expert, but looks like its running out of fuel up top.
Do you have a surge tank, and what size pump feeds it?
What size fuel lines do you have up to the rail?
Which 3sgte injectors are they (what colour) - Maybe go up to Series 4 Rx7 13BT 550cc
What fuel pressure reg do you have?
Is it rising rate? Is it working / the vacuum line hooked up to good spot?
I had a 13BT do something similar once, turned out to be the facet low pressure pump feeding the surge tank was not up to the task, I swapped it out for a carter hi volume and problem solved.
Speak to the guy who dyno'd it, ask his opinion.
I doubt you would punch through a power run at max rpm and if you were looking low A/F ratio's.
It might be the case where the dyno is a POS and every car that goes on it has similar low A/F read - maybe
I would keep my foot out of it until you get it sorted.