Homebrew PCBs

I'm modifying an Epson Picturemate 200 for direct toner transfer, and 
I have a couple of questions about the ink cartridge that I hope 
someone can answer. The cartridge mounts at the bottom of the printer 
(not on the print head) and seems to have 5 ports. One is for each 
color, and the second goes to a grey tubing. My questions:

1 - Is the grey tubing used to pressurize the cartridge? If so, does 
anyone know the working pressure. I can measure it, if necessary, but 
I'd like some more information before I start mucking with it.

2 - There are 5(?) contacts on the side of the cartridge. I assume 
they detect the presence of the cartridge and the levels of each 
color. Does anyone know what signals are expected from the cartridge 
and how to "cheat" it?

I would like to remove the cartridge and feed the printer head from 
an external reservoir. The print head has 4 sets of 90 piezo jets, 
but I would only need one set at a time.

Thanks for any help or information sources.

Mark