i have watched the video over, and over, the thing i am seeing in the first pass, ( right lane) small amount of slip, which is good with that kind of power, otherwise it would dead hook, wad the tire up and go into shake, next, it hook's and the slick actually lost contact with the track, i am assuming both slicks are doing the same thing, if upon contact being regained, the left side slick make's contact first, then it will push the car to the right. i won't say you don't need to adjust preload, but if it were me i would check the spring tension on the wheelie bars first, soften them up a bit, just to make sure that any preload ajustments i made were not influenced by the wheelie bar ajustments.