[Crimson600+HP]

Having a panhard bar could be part of the problem. If you are attempting high speed runs on an uneven/rough surface (anything but prestine tarmac), you are going to feel squirly in the backend under acceleration. The panhard bar does it best to keep the rear axle planted, but when you go over any type of bump, the travel of the axle is not straight up and down as one unit, it moves in a parabola or an arc. Meaning, both rear wheels do no touch the ground at the same time. IRS cars really don't have this issue and the best thing you can do with the rear is a Watts Link. I have one and it has helped tremoundously with keeping the rear planted, but an IRS will inspire more confidence than the stick axle we have.