Kickdown is at WOT, otherwise, forced down shift/quick up shift is regulated by the control pressure cable tension.

You might try adjusting the throttle position cable from the transmission to the throttle linkage. StarTek outlines the tensioning very elaborately, but all you need to do is ensure you have a "slight" positive pull on the cable at idle throttle position. i.e., if you were to remove the cable end from the throttle linkage, it would return to a "neutral" tension with less than 5MM of cable movement, if that!

Should bring you shift behavior back to stock. The tighter the cable, the longer upshift delay, the more relaxed, the quicker the up shift.

Too tight is not good at all and will dramatically and adversely alter your shift performance.

Good luck!

G