I have a '98 EK hatch with a mini-me setup with a y8 head.

Just earlier today I noticed a really high pitched whistling noise that I think is coming from the passenger side of the engine bay?

Sounds like some sort of vacuum leak or something and I did a quick check of the vacuum lines that were easy to access, didn't get any results.

Did some quick searching and have some leads on possible ideas, like the vacuum screw on the throttle body??? and to try and pull the dip stick and see if the noise goes away?

Im lost....

Any help would be awesome.

Thanks in advance