QTR-Quadtone RIP

Setup: Mac 10.4.3 Epson 7000 w/ K6 inks. QTR version 2.3.5

	Problem: Grainy appearance to the images because of white paper showing through the 
ink, from 30-90% in the tonal scale. I'm using the supplied profiles that come with the latest 
QTR. I have used these profiles both with the default linearization and with after doing my 
own linearizations.
  
    
  Things I've tried: I have replaced the capping station, heads, dampers (bought the machine 
used). I've done the physical and logical adjustments after the new parts were put in. I'm 
using the "better" setting in the printer dialog.
  
 	The issue is not banding. The white paper that shows through the ink is in a 
randomized pattern. It's the pattern made by paper (or lighter ink) showing through the 
pattern of larger, darker dots. I use qtr with a 2200 and K7 and achieve very fine results. I 
believe I have all the print dialogs set correctly. I manage to get it done right with the 
2200  :-)
 	
 	Any idea how I can get better results from this printer/ink/rip combination?