well, I agree with you on the additional vacuum, but I want to hear more opinions on the boost pressure. My car does have additional vaccuum pressure now, but my boost is lower. The only explanation I can think of is that the turbo does not have to work as hard as before to flow the same amount of air, producing a cooler charge. Since the air is not as hot, it is not under as much pressure as before. With this reasoning, the same amount of air is being moved at less pressure.