I've installed this shift kit in my old transmission (pre-3800 series II) and really liked it. It really firms up the shifts and stiffens the shift points. It's not exactly a bang into every gear race kit, but is worth it for the street. If you're installing it yourself, it helps to have a factory service manual with the exploded valve body parts view to make sure everything goes back together the way it came apart. I had a problem with the governer springs that were included with the kit, but I think it was more my problem than the kit. My transmission kept wanting to shift at 4500 rpm,so I changed back to the original springs and it was fine. I believe you can also order a set of governer springs (multiple stiffness pairs) from either Jegs or Summit that will give you more adjustability.
88 GT 3800 Series II Auto
86 SC Iron Duke 5 Speed