Please Help Me With Low Power at 20MPH

[CGSTL]

BMW says my 05 X5 4.4i is operating just as intended and it has all the latest software updates available.

But my problem still isn't fixed and it is close to being unsafe to drive if I have to pull into traffic at speeds between 17 to 22 MPH. Here's the problem:

When rounding a corner at about 20MPH my X stays in 4th gear to conserve fuel (BMW says they try to do obain high average MPG numbers and this is one way they do it.). When I push on the gas pedal I have to press it down more than 50% to get it to get up and go. Otherwise, it just lumbers along at low RPM trying it's hardest to stay in 4th gear even though it's getting increasingly more gas. Finally, when I press far enough, it kicks down 2 gears and properly uses the gas I'm giving it and takes off like a rocket.

I just want it to properly downshift to 3rd instead of bog down while trying to stay in 4th around the corner! I'm starting to get really frustrated also because my Volvo-driving wife keeps saying it's underpowered and unsafe to drive. My 4.4i - underpowered!

Can someone PLEASE tell me how I can change my shift points so I have a steady power band through the 20 MPH range?