One tip for jerky 8L90E no throttle downshift. At least one time each week it helps (at operating temp) to let off the throttle at highway speeds and let it gradually slow down almost to a stop with no brakes. The 8L90E keeps the converter somewhat engaged all of the way down through 3rd then drops to 1st just before stopping. I change all of that when tuning them but for non-tuned 8L90E the no throttle/no brake slow down helps it to remember how much pressure is actually needed to make the downshifts.