AvgU was rising along with File and Irp.
If you open a cmd window and cd to c:\Windows\System32\drivers ... you can run
'findstr /m /l AvgU *.sys'
That should return just the file name of any sys file that contains the literal string 'AvgU'. It returned 'Avgtdix.sys'.
Further googling... Avgtdix.sys is a Network Connection Watcher. This file should NOT be installed on an Exchange Mail Server.
I have uninstalled AVG from the server and installed the Exchange Mail Server version of AVG (paid).
No Avg tags are showing up in the Non-Paged Pool... there's no Online Shield or Email Scanner in this version...
I will have to monitor the server for another few days...