Half throttle boost creep issue.

[travypoo]

While driving in any gear if I accelerate half throttle as soon as I get to 4 and 5 thousand rpm my boost starts to creep up, it almost sounds like my WG is quickly opening and closing and the boost is slowly climbing. Since I am half throttle im not overboosting, the boost is just spiking up. it will be at 9, then 11, then 13, then 15. But if I have the pedal to the floor it holds solid at 17 psi and will never go over. Here is a list of mods I have done that would possibly be an issue. Thanks for the help!

-Turbosmart 38mm external gate with screamer pipe
-AEM tru boost EBC (there are 2 different diagrams, one for internal gate, and one for external, if my vac lines are set up for external i have massive boost creep at WOT, so the controller is set up for internal)
-Megan bottom mount manifold(gate flange is welded directly above t2 flange)
-GT2871 .64 (when i first put the turbo on the car it had huge boost creep, so i went with an external gate)
-Vac nipple right above the turbo for the EBC solenoid

http://img.photobucket.com/albums/v4...ture004-10.jpg