Digital BW, The Print

Actually there could be another reason for my failure with the C86:

The black was recognized, but didn't print: should I have removed the plastic cap that is over the "vent" hole labelled here: http://www.inksupply.com/instructions_epson_c84_r200_r300_r800_r2400.cfm 

Or would I damage the  cartridge? The other EZ-N carts weren't recognized, perhaps their chips need resetting? Also, while trying to debug this, I placed the K cart in the C or M slot... no love, did I now mess up its chip too? I wonder if cleaning the nozzle with some MIS cleaning fluid would help?

So things might not be as hopeless as I thought for my C86?

What do you guys think?

Thanks again!
Gianguido