"Jeffrey M. Borning" wrote:
... I kind of hate to hack up a new
compressor, but if it doesn't work, it doesn't do me any good. ...

Indeed. And if it doesn't work, you've wasted your time and money on
the "fix".

Can you hook a manual unloader, just to try it? Disconnect the unloader
line from it's valve and attach a hand/manual valve to the line. Open
the valve until the compressor is up to full speed then close it. Be
sure to open it again when the compressor stops. Bob