Anytime you floor it when it's about mid throttle you're going to see it go high then come back down just a tad. If you were to do this in 5th gear on the highway you may see it more. The boost solenoid is trying to counteract the increase in boost but it can go high and come back down. I don't think its anythign to worry about. Boost spike would be when it goes higher than target at full throttle, but its very noticable if you hit fuel cut.. Just make sure it's not boosting over what it's max boost would be and your'e fine.
Anyone else correct me if I'm wrong