What's harder on the engine?
 

9 psi pulley at 6600 rpm or the 8 psi pulley at 7000 rpm? I actually hit 9 psi at 7k rpm today with the stock 8 psi pulley. That was a record, but I usually get 8.5 psi at 7k rpm.

Take your pick. Torque is where your peak cylinder pressure is so the pressure at that is more important than at redline(with this much boost assuming you are pulling timing).