This is an 06 with a 5.4. Any one know what this might be. Perhaps it has been asked before, but I searched around and found nothing. Any way. I have an AIRAID CAI. And since placing it on, at certain RPM's there is a significant buzzing sound. Generally it is when the engine starts to work a bit harder(say like going up a slight hill, but before it shifts down. Where generally a CAI will just sound throaty. It does not really seem to sap power. I have an EDGE tuner on the track as well. But it buzzed before I put it on. Buzzes a little worse at setting one than stock. Worse yet at Setting 2. I haven't done anything in setting 3. I've checked a rechecked all fittings etc.. I've always had CAI's on vehicles, this is the first one making this sound. Just seeing if any one else has ran into it.

 

If all the fittings are tight, I'd say look around on the filter. You might have a tear in the filter some place.

 

From what you say it seems that the CAI buzzes more when there is greater pressure within the intake manifold. Now I do not know much about AIRAID products, but my guess is that the CAI could be coming loose from the truck body (that is if, in fact, there are no air leaks, as you said, within the CAI body). I guess I'm picturing your truck engine with the CAI on there and the intake sucking down on the CAI so much that it buzzes because the CAI is not held down onto the truck body mounts strong enough.
Another idea is perhaps there is some sort of blockage in the fender well where the intake is getting cold air from (if the AIRAID uses that hole, like I said, I don't know much about AIRAID products). I get leaves and other plant junk in there all the time; some people even say they get mud in theirs.
If all that stuff checks out then look at your engine oil dip stick holder tube and also the transmission dipstick holder tube. They can come loose and when they do they make a tapping and buzzing-like sound, especially when the engine is under more load. The tubes sit very close to the engine, really they are touching in certain parts and they cause some noise. Try tightening them down.
Other than that something must be loose. Inspect at all angles as possible.

Oh yeah, and it could definitely be the filter too like fire said.

 

Thanks all, I'll definately check the filter. Never really thought of that, as it is pretty new, and has done it since brand new. It is definately a loud annoying noise. It is odd. Sounds normal all the time until the engine gets under load, then it sounds like a bee enters your ear.