Need help, I've ran out of ideas..

Ok guys bear with me here I have alot to say and I would appreciate some help. Recently my car has been dipping into the low rpms after I rev the motor and then spiking back up to normal idle. I first tried to just clean my IACV but that didn't do the trick, so I purchased a new one, which was not a motorcraft one it was a BWD brand from orileys. Along with this I also bought the accufab 70mm TB and plenum combo off AM. I installed them all today, and I put in the normal IACV gasket, not the restrictive one to make the hanging rpms go away, because i tried to use that gasket but the car would idle at 1300 rpms where before with the stock plenum and TB it idled fine. I have an o/r prochamber midpipe and borla stinger catback on the car, along with a cold air intake and steeda underdrive pullies. I also have the car tuned with my Bama handheld tuner. After having everything installed and the car running, I noticed that even with the new IACV the rpms still dip after revving. Also now a new sound has showed up, when I'm slowing down and push the clutch in when the rpms hang I can hear almost like a humming/howl/vibration sound coming from upfront where the instake is. And when I rev the car to 2k rpms it makes the noise and right before the rpms start to decent I hear almost like a Sneezing or quiet blowoff sound before the rpms drop. I made a videa here for everyone to see and help try and fix my trouble. Help is really appreciated I'm gettin a big headache over all of this. Please help and give me some things to try.

Also the rattling sound in the video is my U Joints I believe.

Link to Video ---> ‪YamahaEnergy's Channel‬‏ - YouTube

Thanks, I will try the PCV valve thing you suggested and also yes my MAF is stock, is there a certain way to clean it that I should follow by? and what do you think the howl kinda sound is that I'm hearing? is it just a noise that comes along with more airflow from the TB and plenum?

Well i solved one problem which was the humming, it was the faulty IACV I just bought from orileys. Well taking that back and getting myself an actual IACV udner the motorcraft brand, paying the extra bucks for a better quality part. Hopefully that will fix the idle going low, since the one i just bought wouldn't because it was faulty in the first place..

At first I thought actually getting the car tuned would fix it but it didnt, Thats some of the reason why I got a tuner so I dont think thats the reason, and I have not checked the plugs, tomorrow I'm going to order a new functional IACV the one I bought was faulty so I'll find out