If you install the mechanical shift kit, the shifts with become more firm depending on throttle position.
If you simply increase the line pressure, the shifts will be firm even at light throttle applications. I find this annoying, particularly when downshifting.
I specifically told INTENSE not to increase my line pressure with the PCM because I have the mechanical shift kit.
I liked the Transceptor, that I lent to Shadd until he gets his trani rebuilt, because it can boost the line pressure by simply turning a dial for that bang screech racing mode......but I wouldn't want this for daily driving.