Head studs are to decrease the likelihood of the head lifting due to the bolts stretching when high cylinder pressures occur. BMEP (brake mean effective pressure) is the important variable here. BMEP goes up with high boost pressures. It also varies with rpm but usually does not achieve its maximum at high rpm. Detonation also can induce an extreme spilke in cylinder pressures.

 

Like everyone says, it's cheap insurance!

 

I'm only running 21psi sometimes 22 and I went with new studs when I had my cams installed. It's a good idea for the price.