Digital BW, The Print

I have a new Epson R220 in which I am using MIS PRO ink in place of Epson's. I'm using MIS 
spongeless cartridges, MIS PRO color inks that I use with my Epson 2200, and the R220 
chips. With a homemade profile the colors are very good.

Although the Mac R220 driver has a "Black" ink choice ("Black" or "Color"), when I use it with a 
greyscale image I get only the faintest hint of an image on the paper. Using "Color" I get 
monochrome, but pretty clearly accomplished by a mix of colours.

I've tried every combination of 16-bit, 8-bit, greyscale and RGB, and still the "Black" choice 
gives me almost no image (unlike my C86 and C88, which produce rather nice Eboni black 
only prints).  A nozzle check indicates that black is printing perfectly. A search of 
DigitalBlackandWhiteThePrint archives didn't help, either.

Any suggestions?