Lol, we used to have shift kits at times available that reminded me of the old IBM punch cards that altered the performance of your automatic transmission. Do you recall those as well?
I had a 1990 Ford 460 V8 E350 motorhome once and it had the E4OD trans. I put a shift kit on it for $100, think from Banks company. It frimed up the shifting. My 2000 Chevy motorhome (also a van chassis cab) has a 454V8 and shifts great without any kit.
Never put a shift kit on anything else, well the 3.0 1992 Aerostar but it was a funky B&M kit that basically made a slight and adjustable vacuum leak with the adjustment knob in the cab. Kind of weird. I did not keep it installed for long.
Back in the 1970s the shift kit was to fenagle the gas pedal to make it upshift. Been some time but I think it was you are leaning on the pedal, then quidkly let up and press back down but not quite as hard. Then you got to run it with lower rpm while still accelerating some, but not winding it out.
The Aerostar was funky because if you put a bit too much pedal it would downshift, sometimes a couple gears worth, when you really wanted it to stay in the gear it was in. I attribute that to the weak power output of that engine.
I am pleased with wife's 2008 Mazda 5. Shifts well and never aggravates me. Has a paddle I tried once but it was counter intuitive for me a manual transmission guy (my personal vehicle has been manual since 1977).