Hesitation after burnout.

Since loose distributors will move in the direction of retarding timing, something else probably moved the distributor in the advance direction.

Hansen ought to look at where the vacuum advance pod is pointing and see if it possibly hit something like the firewall as the engine moved while doing those donuts and burnouts. I've had this happen in a rally car slamming over a huge rock... knocked the distributor vacuum pod into the frame rail and advanced timing about 40*!