what is that? do i need it?

[tim_blair]

on my black top
there is a black plastic cylinder thing by my coil it only seems to have a vac pipe going to it and another pipe that connects to one to the steel ones that go under the car

what is it?
what does it do?
do i need it?

[sergei]

I assume you are talking about charcoal canister.
it is there to take care of fuel evaporation from the tank.
It is not heavy so best to just leave it in.