2 things mate......
if you're running 10psi, the car is NOT standard. standard boost on an AGU is only 6-7psi at absolute most. 10psi isn't high enough to imply it's been mapped, but it's definately not standard.
Also, if you're getting any flutter when you back off, your DV is broken. SImples. Flutter is compressor stall, and is a REALLY bad thing for the ko3. a flutter means the diaphram is split and the DV isn't opening. This will give you REALLY bad fuel economy. poor throttle response, and generally is *****.
otherwise, good job!