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Help Please! Rpm/shifting Issue

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Hello everyone!

First time poster, long time lurker and I was hoping I could maybe get some help from you all as I'm running out of ideas.

I'm having some RPM/shifting issues with 08 ISF. Here are the symptoms so far:

  • Unnaturally high RPMs in Neutral/Park whether on a cold start or after being warmed up. Drop back down in Reverse/Drive.
  • Standing
    up hill, if I put the car in neutral and let off the brake, it wont
    roll back until I tap the gas. It will then rollback for a second and
    then stop once again.
  • RPMs have to go much higher than before to shift into 2nd, 3rd, etc gear and the car jerks during the lower gears.
  • When
    in bumper to bumper traffic the jerking is much more noticeable as the
    car keeps shifting between low gears. (I drive in chicago traffic into
    the city for work so it gets old quick haha)
  • Under wide open
    throttle and then release the RPMs will drop very quickly but then once
    they hit 2-3k they will hang and bounce up before going back down. Never
    did this early on when I bought the car.
  • When releasing
    throttle, the car decelerates very slowly and wont come to a complete
    stop until the brake is fully pressed down and brake has
    pressure/pushback even when at a stop and car will lunge forward
    slightly when brake is released.

Here's what I've checked/had done.

  • Replaced throttle body, problem continued, put old one back.
  • Checked for vacuum leaks, apparently none.
  • Had transmission reflashed at dealer, same problem.
  • Had ECU reset, same problem.
  • Had data logged/read for an hour, nothing out of ordinary apparently.
  • Only thing that's obvious is that one of my cats is a bit clogged but mechanic friend said it shouldn't be causing it.
  • Also said MAF should not be issue either.

idea what it could be and it's been driving (haha a pun) me nuts. It's
my daily driver too so this worries me every day. To top it off, no
check engine light so I'm completely in the dark!

Thanks in advance everyone! Hope I can figure out an answer soon.

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