Digital BW, The Print

I seem to have no luck with digital black & white.

I started with the Piezography system on an 1160 printer.  Got beautiful, stunning results.  But after a few months the dreaded "Density Shift Syndrome" (DSS) set in with severely washed out midtones and a greenish cast.  Inkjet mall was very good about sending me replacement cartridges for my CIS system.  I reinstalled Piezo inks in a new 1160 and got beautiful results again....for about 4-6 weeks.  Then signs of DSS appeared in the new printer.  I reluctantly decided to throw in the towel with Piezo inks and give MIS FS inks a try after reading so many good things about them in this group.

Today I hooked up new cartridges on my CIS system,filled them with new MIS FS ink, and got perfect nozzle checks the first time.  Then I tried printing only to discover that I still have absolutely no density in the mid-tones.  The prints are actually worse than my worst Piezo DSS prints - almost solarized.

I just printed a gray-scale step-wedge and found that things appear normal from about 0% to around 30% and from about 85-90% to 100%.  But from about 35% to 80% things are a real mess.  There's a catastrophic drop in density from 85% to 80%, no discernable difference in density from about 60% to 80%, and the density at 50-55% is actually greater than from 60% to 80%.

What is going on?  If any of you can give me some guidance, I'd appreciate it very much.  To help eliminate some variables:

1. I am printing on the right side of the paper (I'm using EAM with the logo on the back).
2.  I double and triple-checked the inks before loading my CIS system.  I am certain that I loaded the inks, as labeled by MIS, in the right positions.

Here's what I'm afraid of.  Could a severe case of DSS with the Piezo inks have done permanent damage o my print head?  I did put the MIS inks into the 1160 that had a very bad case of DSS, but I have run a full set of Epson cartridges through it since then and it seemed to be printing just fine with the color inks (although I didn't ever print anything too critical with it and carefully analyze the results).

Any thoughts, suggestions, advice, etc. would be appreciated.

Thanks,

Jim