I was looking at my Throttle Body this evening and I was wondering what the middle port (I will use the word "port" for lack of a better word) is for...

On the side of my throttle body (side with the TPS) I have 3 pipes sticking off...

Top one goes to my passenger side valve cover and is connected.

Bottom one is the coolant passage which I have by-passed.

The middle one definitely has vacuum (with the engine running I pulled the plug off ,you could feel the suction and the engine's idle went all screwy). I don't know where it was suppose to go. When I bought the car the previous owner had a rubber hose pushed on over it and blocked off... see pic

Older pic of my engine bay



Since the hose was a bit of an eye sore I removed it and slipped a rubber plug over it... I never clamped the plug so it just slides on there....it don't fall off but it it certainly can't be tight and I figure I must be losing some vacuum through here...

Can anyone help figure out what was supposed to be plugged into this??? Is it in anyway robbing me of HP/performance?

Can I just leave this the way it is...can I just clamp the hose and not worry about it?

For what it's worth my car did have A.I.R./Smog but it was disconnected before I bought the car...

That one would be going to your charcoal canister if it was installed.

Yep

If you have the canister, it'll be opposite the battery in the front of the engine bay. It's a cylinder about 10" tall.

You shouldnt be losing any vacuum. When the vacuum pulls it will pull the rubber plug tighter to the port.

Hummmm... I have the charcoal canister (it's on the drivers side right up front) but it has a vacuum line already plugged into it... weird....I'm going to have to look at that canister to see where it plugs into on the engine to get vacuum...

Can I just remove this canister all together? I mean I don't have any smog/AIR stuff on the car anymore... is there any reason I need to have that canister?

The charcoal can takes in the vapors from the fuel tank and then let those vapors get sucked back into the engine via vacuum. You can remove it; fuel vapors would get vented to the atmosphere. But, to me, it falls in line with PCV, as a part that does good, with no ill effects.

If you do pull it though, vent the line to a place where fumes won't accumulate.

When I still had my stock intake, the coal canister used a hard plastic vacuum line that was routed underneath the TB, and then pulled a 180* hook and plugged into that TB port.