It's the trans kickdown function that's getting in your way. When you put your foot down you'll notice you hit a resistance spot just before the floor. That's where the kickdown cable stops lifting the upshift pawl in the trans and lifts the downshift mechanism (don't know if I got that precisely right). If you stop at this point you won't kick down. Unfortunately the throttle won't quite be open all the way, but darn close. Playing with downshift cable adjustment to overcone this will just give you grief for normal shifting. If you need better performance then you'll want a manual trans.
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Dave -own 940's, prev 740/240/140/120 & quasi-expert only on a good day