What is this? It seems to be the cause of my whistling/humming problem. I'm not talking about the butterfly

 

What do you mean whistling humming problem. That part is for the IACV and is necessary to be there.

 

I figured that the slot needed to be there. A couple of weeks ago I noticed a humming noise coming from the intake. I had just put in a K&N filter so at first I thought that was the problem. I disected everything yesterday and could hear a whistling sound coming from the slot in the throttle body. When I put the intake tube on, the noise is more of a humming sound. I did make sure that the butterfly wasn't making the noise because it was completely close.

 

Its a normal noise, not a problem. Its part of the reason our cars have a few resonators on the intake.

 

The noise wasn't there after I removed the resonators which was 9 months ago. It just recently started. I'm wondering if it could be a carbon build up in the air path which is causing the noise. It's embarrassingly loud. I may try to remove the IACV and clean it.

 

You didnt hear it, or you have a hole/leak in the air system because ALL 2nd gens have it. Its a characteristic of the motor. Its not a buildup or any thing. Adding the K&N may be why your hearing it more as its allowing more flow/noise.

 

The K&N has nothing to do with it because the sound is just as loud with just the intake pipe connected to the throttle body - without the other end connected to the air box

 

If it's machined in, it was there before you had the noise. Something else has changed, I doubt the slot is the problem. Something else You've done is likely the issue.

 

Well all i can say is your car made the noise before hand. You dont have a problem because all of our cars make it.