Digital BW, The Print

I've had my R220 for about 5 months and recently, sometime after switching to glossy 
papers and PK ink, started noticing faint light lines in areas of high density blacks and 
low-mids, in the direction of print head travel.  They're very faint, not really noticable in 
normal room lighting or beyond about arm's length.  Wondering if others have noticed this 
and if there's anything to be done.

At first I thought this was due to clogged nozzles, but I clean (and align) the heads 
regularly and get good nozzle check prints.  I tried "Super Microweave" on one print, which 
largely seemed to take care of the problem but at the expense of a quadrupling of print 
time.  Do others use Super Microweave on this or other Epson printers (I don't see it 
discussed much here)?

When I was using MK with matte papers, and with PK on newer cotton-based glossy 
papers such as CMSR and the Innova F-type, I don't see this problem (presumably because 
the dot gain is higher for cotton papers and the adjacent printed lines "blend" as they are 
laid down and soak into the paper).  This only seems to happen with RC-type Epson 
semigloss papers such as PSG, Luster and Semimatte.  Is this more or less normal and I 
should learn to live with it for these paper types or is something more sinister at work 
here?  I use MIS UT-R2 inks by the way and print B&W exclusively with this printer.  Thanks 
for any help or ideas.

--Geoff