So i found the solution to this ANNOYING issue, castrol multi-vehicle import ATF was put in before via drain and refill x3 and it barely improved the issue, but i changed the transmission filter, thoroughly cleaned the transmission oil pan and the three magnets inside that catch any metal shavings with gasoline and then power washed it with water, and then poured the (very clean) tranny fluid into a 5 jug quart to measure the amount i had lost (when taking off the tranny pan some fluid will come out please have a oil pan under neath to catch all of the fluid and also fluid will come out as you take off the tranny filter as well.) about 3.2 quartz of tranny fluid came out, i poured in 3 quartz of AMSOIL Signature Series ATF, WOW driving afterwards the car shifted so smoothly, castrol multi-vehicle import ATF is great fluid i put it in my 2001 GT auto tranny and that car shifts so smoothly i can't even tell when it up or down shifts but, that same fluid didn't do much in the GTS auto tranny but AMSOIL worked, i am an AMSOIL Signature Series ATF fan for life now, i think if you have a jerk or a slight hard shift, and no other fluid fixes it, this fluid is worth a shot as it worked for me like a charm.
