Rick , Setup does not sound bad. You don't have your droop setting, as others have suggested if you are running 3mm or more try reducing the front droop. If you are running 1-2mm now then try taking out the 2mm spacer under the rear hub link. Also try adding a red bar only on the rear.
You might also try adding a touch of anti-squat (.7mm)it is double edged though as it will loosen the car a touch off power.
Martin commented also trying the 8d caster block from the 04 it will also help slow the car response and straightline stability.
Not sure of the grip level on the surface if it is pretty good you might also try the 2 hole piston the 3 hole with no bars lets weight move quite a bit on the car, it could be making the car bite the surface just too much. I was messing with my car yesterday at home going back and forth between the 2-3 hole pistons and there is quite a bit of difference in dampening and pack.
Try some of these and let us know what helps.
Also what insert on the A's?
Tamiyadriver look back a bit on the diff Martin has built it and it works well HPI pro2 outdrives.