Turbo not boosting while jaking.

[Jprps]

Cm871, de-mandated, tuned by a respected member here.
So I put a turbo charger on my truck a couple months ago, everything has been working well until last week or so, turbo makes a bad squeel sound when jaking. (I assume its the turbo to manifold gasket as I've had this sound before and that was the problem) which isn't a big deal but today it threw a code for vgt (2387 i think) and before I rolled into where I was going it wouldn't make anything above 10 lbs boost when jaking. It seems to spool up fine when accelerating but not when jaking. I did notice the last couple days when jaking the turbo seemed to opening and closing ever so slightly when jaking hard, I could hear it happening.

Any ideas on where to start? Will that gasket cause this to happen if its leaking exhaust bad? Or maybe I got a sensor or something that needs replacing? Maybe the turbo actuator is out of calibration? Any insight is appreciated.