It is the charcoal canister and it actually sits to the right of your battery. There are four lines total attached to it, the one seperate one ontop is the line to the gas tank that transports the gas fumes to the canister, the two lines that are together are the purge line and the signal line, they are both connected to the throttle valve and the little one is the signal line, when the throttle valve opens and supplies vacuum to the little one it will open the vacuum valve on the top of the canister and allow the gas fumes to flow through the larger hose and into the throttle valve and into the engine. The big hose on the bottom is the vent hose that allows fresh air into the canister as it is being purged. I have never tried blowing air into one but it stands to reason that you should be able to force air through all but one of the fittings, the signal line I think would not flow air but the vent, supply, and purge lines should flow at least some air through them.