Replaced actuators.....now this...Need imput.

[Rig Wrench]

No vgt calibration for the 870. Just bolt on and go. I don't blame you for goin to hx60 if your turbo is bad. Good or bad programming, stock or otherwise, the air vgt don't seem to live as long a life as the electronic do. A long lasting one tends to be more the exception than the rule.
Insite does have a turbo travel test you can perform. You may need disassembly to find the issue though. This sounds like a possible imap sensor on the fritz though. had one play games on me a while back. Showed 5lbs of boost not even running, just with key on.
I believe properly tuned the hx60 will return as good if not better mileage than the air vgt, and if your looking to make big power, probly better off. I will be doing this swap on a 565 in a Pete before too long. I'll be sure to post results