Your video would have been allot more telling without the music.
85's seem to shift a whole lot smoother and more like a "real car" than other years. Allot has to do with the blue flying saucer. I know my '85 shifts perfectly so I have never ever touched anything. {it came that way}
My '81 shifts a LOT harder, and shifting is
really dependent on accelerator position. It will shift quite a bit sooner with less pedal, which I'm sure is Bowden cable related. I need to soften the shifts a bit with the modulator {on back of IP, not on tranny} but have just never pried that cover off and tried adjusting it. I'm happy enough with it's operation that I haven't messed with it.
Next video you post let us just hear the car. Is your blue flying saucer still connected? You should be able to dial your shifting in to where you like it.