anybody ID these fittings on my plenum?
 

I think it's an 88 IROC TPI. I think the nippple go to the brake booster, but what went in the large threaded hole? Looks like 3/8" NPT to me. I've already (I think) accounted for all the other connections. Any bright ideas, wild guesses, internet wisdom?

Re: anybody ID these fittings on my plenum?
 

I believe that is for the IAT sensor.

Re: anybody ID these fittings on my plenum?
 

To pick nits, it is the MAT sensor... Manifold Air Temp, not Intake Air Temp. The IAT typically has an open element that needs the clean air after the air cleaner, and before EGR and/or PCV are added and could foul it inside the manifold. The MAT sensor is closed, just like a coolant sensor and won't get fouled with EGR/PCV.

Re: anybody ID these fittings on my plenum?
 

excellent, thanks guys. my setup is going to have the plug-in IAT open sensor on the rubber elbow on the front of the throttle body, so I'm going to fix this with a pipe plug. :)