Suspension Problem

I had the opportunity earlier this year to drive my GT5 Bullfrog at speed on the Texas World Speedway. I had driven the car into triple digit speed zone previously without incident. However, the TWS front straight invited going a bit quicker than previously.

I'm hypothesizing my speed was 120MPH plus when the front end of the car began oscillating up and down. I would opine that the condition seemed to become more exaggerated, although, I immediately backed off the throttle to bring the car back under control. This was a bizarre experience that I had never encountered before.

It reminded me of an documentary that I saw on TV about the design and construction of the Ford GT. When they were tuning the shocks for the car, they mounted the GT to a moving platform that would simulate various irregular road conditions. The initial shock set-up created a similar oscillation that, once started, continued to compound and get worse.

On my Pantera, I am running Carrera shocks. They came with silly soft springs. I am working from a bad memory when I guess that I have 700lb springs in the rear and 800lb springs in the front.

I realize that stiffer springs up front are not the norm. The stiff front springs were to reduce wheel/tire travel in the front to reduce the likelihood of the front tires hitting the flares. The combo has felt fine around town. Yes, I should create a better bump stop for the shock.

Regardless, do any of you suspension gurus have an insight as to what is going on and causing the up and down oscillation? Suggested cures?
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