Digital BW, The Print

I have a 1270 loaded with MediaStreet dye ink and a CFS. Nozzle checks
are perfect and will print letter size perfectly. Soon as I try 13 x
19", I get some nozzles dropping out. Specifically, black and cyan. The
nozzle check will sometimes show some black ink lines mixed in with the
cyan line position when this happens. (cartridge problem?) I have
already wrecked 5 13x19's this way. Soon as it happens, I run a nozzle
check and usually one cleaning cycle will do it for a perfect nozzle
check. I can then print letter size with no problem, but then 13x19"
turns up the problem again. I tried raising the bottles a little, but
this gave me another problem of ink blotches, so I put them back down. I
am beginning to think that the CFS is to blame and for some reason can't
keep up the inkflow with the larger papers being printed. Anyone have
something similar happen? 

Murray Z.