Need help, recently got a light for code P2279 (intake system leak)

I drive a 2018 a6 3.0t. A few days ago my car started to make a whistle sound but only at night after I’ve driven quite a bit. Sometimes it’ll happen when I’m idle or stopped and sometimes it doesn’t at all but it almost always happens when the car is rolling into turn or stop. I read online that it’s most likely the PCV failing and so I started it without the oil cap but the sound continued which I believe means it isn’t the PCV. The sound is louder some days or quieter. Just last night I got a check engine light and it was for an intake system leak. I did put a cts intake on it months ago so I checked that for any leaks or breaks but found nothing. If anyone has run into this issue please help me out, I’m not sure where to start checking for problems.