I bought my 01 GT used recently and it came with afternarket Eagle alloy rims with new tires. I noticed almost immediately that the steering wheel would shimmy back and forth roughly between 45 mph and 55 mph. The gear shifter does the same thing. It seems that it moves faster and slower with the speed of the car. I took the car and had the front end alligned and the new tires re balanced. The tech could not find the problem, the car still does it. The tech said that the tires and wheels seem fine. He also rotated them front to back, but this did not help. The rest of the car is basically stock right now. What is the problem? Maybe the stock driveshaft?