Search on DSMTuners, theres a big thread about auto tranny compatibility. I know you cant use a turbo auto tranny on a NT car without using the Turbo TCU. My EX GF's NT Talon tranny was starting to slip and we went through this exact same thing. She ended up selling the car before it went out so I never actually replaced it, Just did some research on it.
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I used to have a 420A...
'92 TSi AWD
11.8 @ 119mph 470awhp 405 ft/lb torque 30psi on E85 w/ Borg Warner S256 Turbo