Thanks for the reply.
The options for my printer driver are a little different from those on the link you gave me, but close enough that I think I chose the correct settings. I also played with the contrast and darkness settings. And forcing black/white (versus Auto). And a couple of other settings. And none of it affected the output.
I tried a test using graphics, not text, and there WERE some subtle changes to colors, including black. Not much difference between +8 and -8, but visible.
Before posting to this site, I tried calling the support number (the same one you listed). After working through the automated menus, I was told that this printer is supported online only. Couldn't talk with a person.