You are on the right track, I think the changes you made will help.
I played with this a lot on my F.A.S.T. GTX. Running 10's on stock suspension and G70-14 Coker redlines, I found that the car needs to be level sitting still, level (side to side) at launch, and have a lot more weight on the LF and RR to keep it from lifting the RR tire and loosing traction. Solution: add leaves or half leafs to the RR spring, crank up the LF torsion bar, get the weight on the RR and LF tires. Then loosen the RF torsion bar and de-arch the LR spring to get the car level and drop it down to the proper ride height.