One thing to keep in mind is manually shifting into 1, 2, or 3 pulls it out of auto, and it will not downshift even at wide-open-throttle.
The Ford transmissions actually tend to shift early. You can take advantage of the high end HP by holding a lower gear than normal. 5,000 RPM in the V10 won't hurt a thing.
What year is your chassis? There were some 2009's that had an obstructed air intake, and Ford will fix that.
25 MPH does sounds slow, but at higher elevations that could be normal, simply because of the lack of air.