Just installed MPS Dual Matt Piezo carts. Used OEM Epson chips from 3880 carts. All carts appear to print correctly except Y cart with shade 7 which prints pink. I printed out a 8 color flush chart too see this condition. Pulled the Y cart and made a smear with a q-tip which indicated the ink was indeed Shade 7. Yet when I print an image with 3880 Quad K7 there is a decidedly pinkish cast in the highlights which I believe is coming from the Y cart. Looking for an answer to clear up this problem.
Did you ever have PiezoFlush in the printer? It does sound like there is PiezoFlush in that ink line. Probably two POWER CLEANS will push any remaining flush fluid through. Could you do that and let us know if that fixes it.