sounds like the pot may have a dead spot in it. When it does not want to accelerate will it move if you smash the pedal? If i does that makes me believe the pot is bad. The transmission that is a weird problem ive never encountered it but it either may be a glitch in the shifter assembly its self or in the plate in the trans.

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1982 300D Turbo (Mom's)
1993 BMW 525I (Dad's)
2001 Vw Golf (Brothers)
2002 Nissan Ser SpecV (Im the Black sheep lol)