Update:
The temps hit ~ 80 today, not blazing hot, but warm enough to make the cabin pretty hot when I went out for lunch today. I have to say, it actually cooled down fairly quickly. I didn’t have a thermometer on me but it definitely felt reasonably cool, reasonably quick.
When I tested the vent temps the other week, it was with the truck idling in park. I can definitely notice a huge difference in the AC whilst the truck is driving versus idling (of course).
It almost felt adequate. It’s still not going to win any awards, but perhaps it was worth having the TSB done after all.