thanks, I cleaned the heads again. It seems like thats all I ever do with this cis system. Changing the preferences to 'Artisan Premium' makes it come out darker. I also took the 'high speed print' setting off. I think that also helped.
The print is dark, but when I hold it up to the light, you can still see through it. Will I have to double up transparencies, or am I preparing the file wrong?
If you are not using an all black system, you may want to try a test printing in 100% K instead of rich black. In Illustrator I think the settings I usually use are 720 x 720 dpi Premium Glossy Photo Paper (250) for the resolution and media. Under Print Settings, Color set to black, and Print quality set to Superfine 1440 dpi., High speed unchecked.
On that note, I believe there is an option that is on by default in illustrator that forces black to output to rich black whether you want it to or not. You might want to check your settings.
I forgot that you are using a cis. That might be your problem as well. I recall someone I know having really bad banding when using a cis, but it magically went away when they went back to the oem cartridges.