Based on that description of your typical speeds, sounds like the pedal / TPS fix may get you into top gear/torque converter lockup sooner & more often.
Unfortunately it doesn't. The torque converter still doesn't lockup until 45. But at least now I can feel a pronounced up-shift into fourth gear sooner, at about 32 MPH rather than 38. So there is some improvement in the way it is shifts, and it's now more in line with the manufacturer's specs.

If we return to the applicable graph of shift points:

download/file.php?id=919&mode=view

we see the lockup mode (4L) illustrated on the map. According to the chart the lowest speed at which it can ever enter lockup is at about 42 MPH (68 KPH on the graph). Also, according to the graph, it will drop out of lockout mode unless a constant speed of about 40 MPH is maintained. Apparently that's the way it was designed, and there's no way to change it.

All our local speed limits are 40 MPH at most, and that's about what traffic on the road averages - so I can't go any faster than the car in front of me. If it were to enter lockup at 40, as my other car does, it would be better. Yes, that few MPH difference matters in my case. I guess I could call it the Chevy disadvantage.