The MAAM DC3/C47 bundle is giving the same problem. If you do not install FSsound.dll but selected to not install the file as optional asked in the warning message you get when starting FS, you simply will not see all the gauges. It's mentioned in the manual :) .
And indeed it's solved with the additional item in FS9.CFG.
I think this applies to your problem too. So you better reinstall the FSsound.dll file and make the addition in your FS9.CFG file.
However.
There seem to be a new version of the FSSound dll file, v1.6 (beta ). Check at ftp://fssound.hn.org/FSSound/v1.6/FSSound160beta1.zip. This file too will cure the problem of the false warnings (with thanks to the MAAM team for supplying this information).
Grt.
Paul.