Bizarre boost issue, HELP!

I have never seen this kind of boost issue before. It's not limp mode, and it is totally consistent, no change w restarting car, etc.

It's a 2011 TDI with a Malone stage 2 tune, all emissions deleted.

What happens is there seems to be very little boost until about 2500 rpm, then normal-ish boost from 2500-3500 rpm, then boost drops back off again. No CEL, no change at all w/ restart, unplugging battery, etc. No obvious issue in the engine bay.

Another thing: The turbo makes very odd whooshing sounds now, like the wastegate/bypass is acting up.

Can anyone point me in the right direction?

Thanks all!