Turbo surging ??

[davebow]

I just got done putting my 05 CCLB together last weekend from doing studs, bullet proof oil cooler, coolant filter, and every factory updated or upgraded part that I could find. In the process, I put on a 4" MBRP turbo back exhaust w/ cat delete and 3.5" downpipe and S&B CAI, and replaced all of the CAC boots, serpentine belt, and radiator hoses, disassembled the turbo to clean up the unison ring, vanes etc, and did a CCV mod. The truck is running great, with the exception of what sounds like the turbo surging a bit.
I looked through as many threads as I could find on this issue, and I'm still not sure where to go to get rid of this. It sounds like the turbo is continuously trying to figure out what position the vanes should be in. What I have found is that it is possible the the slot in the unison ring that controls the position of the vanes could be worn, causing the vanes constantly be changing positions. My CTS is showing that the VGT % is constantly fluctuating 2-5% or more whenever the turbo is producing 4 or more lbs of boost. Even under hard acceleration it jumps around the 2-5%. At idle it sets steady at 85%. I understand that the turbo constantly adjusts for engine RPMs, however, is this amount of correction normal. Am I only just now hearing it since I put the S&B on, and it is more noticeable because of that? Is it possible that the exhaust and CAI are flowing so much more air than stock that it is confusing the turbo or maybe causing mild compressor stalls? I'm hoping that Mad or MWilbur will chime in since they have learned so much about turbos over the last few months. Any suggestions on where to look to solve this would be appreciated.

[mhatlen]

Have you taken a look at your egr valve or cleaned it up? Do you have the ability to track desired and position of it? The MAP controls the egr and tells pcm where your boost is at from the intake manifold may be hangin up a bit?
I can tell you the S&B will change the amount of air coming across the maf sensor. You will be a bit more likely to have turbo flutter with aftermarket air intakes, I too have a S&B intake but it's sitting behind my shop at the moment. I would try putting back on the Donaldson filter assy, I know it's not as pretty but it's better for the turbo and less likely to send backpressure into your intake.
Try that first and egr to see if anything changes.