Originally Posted by nerdling

I've been working on a setup on my T3 for carpet/foam racing with a similar problem, mainly the over steering off power. I cured this (really effectively as it turns out) by dialing in some anti drive on the rear (where the front of the rear hinge pins are angled up compared to the chassis). This setting causes the rear to resist unloading during acceleration.

Try this and see how you go. Hopefully you get a car that under-steers but does not over steer under slow down.

Remember, fix one problem at a time.

I also changed to a Front Diff (instead of a Spool) but this won't help with the under-steer.

To address the Under-steer I would install the rear bar, maybe go 1 or 2 steps thicker than standard and see what happens.

Let us know how you go.