4L60e Quick 3-4 Shift

2004 5.3 liter with 4.8 flat tops, .020 over, 6.0 liter cam, stock tune except idle.

Tranny fresh with Z-pak, new sprag, sun shell, all other clutches and steels, Sonnax boost valve, wide 2-4 band, soft parts.

I get a quick, almost non existent 3-4 shift under medium throttle.
Also feels like it's hanging up shifting into 4th as well.

Under granny/grocery throttle position, it shifts thru the gears fine.

It shifted the same before I found out my PCM was swapped out from a 4.8 liter truck.

Can I change some settings to correct this?