I think Chris is right. DME has 2 triggers to go to open loop. 1) TPS signals WOT or 2) AFM door fully open (400-4500rpm?). At open loop the only sensor the DME apparently listens to is coolant temp.
Note tho that long term fuel trim (LTFT) can get you. This is set by O2 sensor and AFM. If your LTFT is goobered up, say it’s too lean, then when you to WOT it’s still going to be too lean.
That said, I’ve never heard of such a big delta between hp and torque so I don’t have any good ideas. I would contact Jim Levie and Chuck Baader and see what they think. You can track them down via the Members link at left. Also, you should post the dyno result. Be sure that it has F/A info. Dyno results w/o F/A are good for compliance, but they don’t tell you much about what’s going on with engine management.
Ideally, you got the dyno data from the shop and can get the software to create graphs at home. This allows you to zero in on different parts of the curve so you can see more detail.
My bet is that this is simply an artifact of the dyno. I think that there is some consensus that Mustang Dynos read lower then Dynojet dynos. I’ve only been on a Mustang dyno once and it was indeed low. Jeff Retey spent some time on a Mustang dyno recently I think. You might ask him about his experience.
Before you spend a bunch of time and energy on the problem, I’d see how hard it would be to get on a local dynojet dyno that other SpecE30 types have been on. You might find that you don’t have a problem.