HELP! Nasty boost spike

[drifter_for_life06]

Alright guys, i jusst got a Hallman ES manual boost controller. Got it installed and on the dyno at my school. When we set the controller, it went to 11psi and that is where i "locked" the controller at. So now im get on the road and im driving, and !wtf!? boost shoots to 15psi then settles back to 10-11psi. It did that for the first day, then it starts going past 15psi then settling. So my question, why is it doing this? I mean i know spikes of a 1psi or so are sometimes common, but 5-6psi?

Also, the other day when the boost spiked there was a very weird noise and feeling. Almost like a fuel cut or no spark maybe or something? I have no clue.

Anyone with any insight to either of these, please post?

Ryan