I have a 2000 Ford Mustang equipped with the 3.8L motor and an automatic transmission. The car has ~250K miles on it and both the engine and trans are original and neither has been rebuilt. The car runs great except for a harsh 1-2 shift. A while back I was driving it and the car felt like it slipped going from first to second. Ever since then it has had a hard shift going from first to second. All other gear changes are smooth. The car shifts hard enough going from first to second that it will chirp the tires if I'm over ~50% throttle. If I baby the throttle the shift isn't as hard but it is still clunky. All of my internet research led me to believe I had a broken 1-2 accumulator spring. I dropped the pan and removed the 1-2 accumulator piston only to find two intact springs and a healthy looking piston. Since I was already in there and had the parts on hand, I replaced the piston, cover, and both springs. The kit I got from CT Powertrain had a purple lower spring and a white upper spring. After I got everything back together I went on a ~30 mile test drive and the car still shifts hard going from 1-2 with no other shifting issues. If I manually force the car to shift from 1-2 using the gear selector the shift is much smoother. I looked at the output of the TPS and MAF using a scan tool and they seem to be working as intended. I even cleaned the MAF to be sure. The trans fluid is Motorcraft Mercon V and is filled to the appropriate level. I'm at a loss on what to do next, any ideas?