I did a gen 3 top swap on my 2000 grand Prix with an xp cam and all the little things to go with it. Lifters. Valve springs. Ported heads. 42.5 lb injectors. Also on a 3.4" pulley. Its on the dyno and everything is reading good except for the power. Its only making 190 something horse to the wheels and a peak of 4.something boost. Timing is at 15 degrees with 0 knock. The boost reading was choppy going up and down during the pulls instead of a straight line like it should. He bypassed the boost solenoid to see if it would make a difference and it didn't. I suggested that the belt could be too big and slipping causing the boost levels being low and the boost levels going up and down. He checked and thought the belt was too big so they ordered a smaller one. Could the belt size cause that much of a power loss? What else could it be??
