Tire pressure, for the most part, is related to the tire size, shape of the carcass, volume of air in the tire, and the load on the tire.
You'd prolly have to experiment, but people who tune cars for a living tend to be anal-retentive about tire pressure. I'm sure they didn't pull 29 out of their butt.
So, I would bet that 29 is a REALLY GOOD place to start if you haven't changed the tire size. The optimum is prolly not far away from it, maybe a PSI or two above or below...