Even on a stock engine, a Tune makes a noticeable difference.

 

If a tune includes increasing line pressure, then installing a shift kit and putting line pressure back to stock is a more efficient route. Increasing line pressure is going to put more strain on the pump and other components, and create additional parasitic drag to operate the pump at that higher pressure.

 

Flipping the 4th servo piston is going to tighten the band up. This might provide a cleaner shift but not a harder shift IMO. Keep in mind that you do not want the band to tight or you will damage your transmission. If you do this adjustment make sure you can turn the output in both directions so we know the input drum is still spinning when the band is not applied.

 

Blackbear for me