OK, I'm very frusterated with my 91 GT. Up until about 65-70mph the car is very smooth and enjoyable. However from about 70 on up my steering wheel bounces up and down way too much to the point where you can actually see it vibrating. It makes the car very unpleasnt to drive at highway speeds. I have H&R Supersport (750 lb) springs in front with Bilstein struts. Also have MM CC plates installed. I have had my tires balaned recently and it did not correct the problem. What could it be? I have driven cars with tires out of balance and this definently doesn't feel like that. The suspension of the car actually feels very smooth at all speeds but just so much vibration is coming through the steering column at 70 plus mph. Any help will be greatly appreciated. Thanks.