The can is to absorb fumes from the fuel tank, which prevents the tank from builing up pressure when it gets warm (primarily when the vehicle is not runing I believe). The carbon holds the fuel fumes until the computer decides to allow the fumes into the intake charge. In the olden days, these fumes used to vent to atmosphere, which is pretty harmful to the environment.
You can remove this system, but I would encourage you not to. You will not see any performance gains, will drop negligable weight, and may trigger the cel.
As far as throwing a CEL, EEC-IV (w/ OBD I) doesn't have any way to monitor evaporative emissions so it can't throw a light. If you live in a strict emission enforcement area though, you may have trouble passing the visual without it being there.
I thought there was a solenoid that controlled when air was allowed to flow from the can to the intake. This is what I was referring to throwing the cel.
I think the only thing that the ECU sees is the solenoid itself. It can throw a code if it doesn't see the solenoid open when it is supposed to. It doesn't know if there's anything attached to the solenoid or not, so in a sense, the canister can be MIA as long as the solenoid is still there and operational.
To answer your last question. We're both half right
i mean, i dont really need to pass smog, there are a lot of russians in new york that will look the other way but i think i am going to order stingers intercooler kit so im probably gonna take it out. thanks for your replies guys.-marcin