[Tom Goldman]

Dave , if the car is launching and going straight up untill the shift, the preload is probably in the ballpark.
I'd loosen the shock, both bump and rebound ,as it sounds like they are too stiff and the tires are breaking loose after the shift.
If your 4 link is set up short and violent for S/G, you may have to lenghten the intersection to run wide open.
If you're planning on running the MASGA race at Cecil, come and see me.
Or PM me if you're not.