Help! Turbo S pulls abruptly to the side on throttle transition.
 

Basically what the title says. It's most noticeable above 45mph. When the throttle is applied, the car will suddenly pull to the right for a brief moment, and when the throttle is released it will suddenly pull left. The movement is very abrupt and destabilizing (and has gotten worse in the last couple weeks), like the whole weight of the car is shifting from one side to the other.

I recently replaced all 4 shocks with OE Koni yellows (inserts up front), replaced front control arm bushings, steering rack bushings, tie rods, and front wheel bearing (the car needed them all). It helped with most of the handling issues but this one problem seems to persist, and I'm starting to think it's not suspension related. My local mechanic is stumped and I don't have any Porsche/import specialists in my area.

Any help in diagnosing this issue would be greatly appreciated.

Something is loose in the rear suspension, causing a change in alignment under torque.

I would look at all the of the bushings around the trailing arm. Both the inner end of the banana arm and the main pivot on the outside of the torsion carrier.

Could it be a transaxle/CV joint/axle/hub, or tire problem.

I had to replace one tire on the rear due to a puncture on a trip, the old tire was very close to time for replacement and just due to the different tire diameters, I could feel it push when I got on the gas. It surprised me that I could feel the difference.

+1 maybe a tire issue. 10-15 pounds low in right rear...?

Tire pressure