Rough Idle, struck at ~1900 before normal, then crashing to ~600

[Benne02]

Hello! As the title suggests I'm having issues with my idle. For some reason it always gets down to about 1900rpm and then sits there for 5 to 10 seconds before moving on down to around 1000rpm. It is like this weather it's standing still or the clutch gets pressed in while driving. (It's been like this for a long time but I have not come around to look into it.) Since I installed an oil catch can and did a liqui-moly clean in the engine before my oil change (not sure if this is the cause or if it has no correlation) the RPM's on idle have been going past 1000rpm and down to around 600rpm, at this rpm the car runs very rough and backfires.

Other things done to the car is a CAI, Exhaust, and SCT tune (have set idle to about 1000rpm in my tune).
We are experiencing what we think is a vacuum leak since the vents for the AC won't open in the cabin, which might cause the low idle, but the vents haven't worked for a long time and this sudden drop of rpm is new. Not sure if a vacuum leak could cause rpm's to get stuck either.

Any help or expertise would be very much appreciated. Thank you!
(Video of idle:

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[ttocs]

to get the vents working, look on the pass side of of the firewall under the hood and by the heater core input/out you will see a vac line hanging down. Look at the vac tree on the drivers side and there will be a hose that goes to it that probably broke on top of the motor. You can use some large tubing as a coupler to fix it

 

[Mike’s4ValveCobra]

My car was running like this a while back and it turned out to be loose hose clamps/air leaks on the cold air intake causing the issue. If there are any vacuum leaks the MAF sensor readings will be off causing idle issues.