It's on the left side of the engine, coming off the intake manifold. Reason I'm asking is because my intercooler piping is so close that it presses and rubs up against it and I'd like to know what it's for so I can get a new one or fix this if need be.

 

How is your idle?

That plug goes to your idle air control valve.

 

It idles alright. Right now I'm running a MAF and I have a BOV on my turbo that dumps into the atmosphere and isn't recirculated back into the intake, so sometimes it's rough and stalls out if I come to a stop too quick. Would it be very noticeable?