So I thought my Forge valve was acting up, but I swapped to the stocker today, and it still does it. It's compressor stall (flutter), but only under vacuum, around 10 inHG. It generally only happens when I back off the throttle. I can provoke it by blipping the throttle sometimes. You can see from the log shot when it happens.

I'm starting to think either there's something going on with the boost solenoid, which is doubtful, or the fact that the MAF is bumping up against the K&N heat shield is starting to cause a problem.

 

Another pic:

 

I posted in HPT dude.