Yeah, this doesn't have anything to do with anything you had done to the transmission. It always stays in 4A like Loki said. It would be nice if it stayed in Sport, but I've heard rumors that they can't stay in drive modes they weren't EPA tested in as default.
Dumb if true, but sounds about right.
Honestly, since moving, I've fallen out of love with my Expy. It was great when I had a 30 minute highway commute and was taking weekend road trips all the time. Now that I moved and all my driving is stoplight to stoplight in the burbs and no road trips due to Corona shutting everything down, it's a big bouncy unwieldy vehicle.
To counter this, I have to put it into sport every time I start the vehicle to firm up the steering and to also get the turbo V6 and the 10 speed tranny to play nice together at non-highway speeds.