Weird whistle, 15 psi max boost?
 

Hey guys I'm a little worried about this.
I recently installed a PDI manifold and 4" exhaust, and the truck ran perfectly afterward. I was seeing about 23-25 psi max with wastegate hose clamped off. A few days ago I wanted to try going fuel-plateless so I took it out (I'd been in there before). The truck started kind of hard and then died after about 20 yards several times, so I put the plate back in and set it full forward. I reassembled and then washed the truck thoroughly including the underbody. I parked it and the next time I went for a ride I started hearing this weird bbbrrrreeeeeeeeeppp sound whenever it built boost, which now was limited to 15 psi. Not like a turbo whistle, and when I open the hood and free rev it it sounds like it comes from the pump side not the turbo.
Any thoughts are appreciated before I open it up again.

Well I took the afc off, took out the plate, couldn't see anything amiss but couldn't see much of anything either. Put it back together and now I can still hear it but it's less intense. Boost is still 16 psi, but that was with the wg untampered with. Also when I'm cruising at 65 mph it only shows about 4-6 psi. I'm used to seeing 8-11 or so on my common rail. Are these numbers about normal or is something screwy?

Boost leak. Probably from the AFC signal line. I'm guessing the dying had something to do with the shutoff solenoid, since you were messing in that area. Explains the low boost and the whistle.

Yep boost leak, a slight reassembly error. Still only makes just over 20 lbs with the hose clamped though. But whatever I'll leave it be for a while.