So...I'm running into a very odd issue and i'm at wit's end to figure it out. Only mod to the car is a makeshift intake, plastic autozone tubing with a cone filter attached and a hole drilled for the sensor. Only work that has been done recently is the PCV valve was changed just because I was in Advance and couldn't remember the last time I changed it. We did try a new one just to make sure I hadn't gotten a faulty one.
The problem : still runs fine, no issues there. BUT it make a very odd semi screeching noise that cannot be isolated to anywhere in the engine bay, also there is the occasional 'chirping' sound.....
The odd part : The car is running, remove the oil filler cap A) there is a strong suction holding the cap on, B) the odd sound stops, and C) the motor runs much better.
My father and I checked around thinking it may be a vacuum leak or a vacuum line is plugged causing a vacuum in valve cover, we checked the majority of vacuum lines we could find/check including the brake booster line etc, no problems found.
Went by Advance Auto and O'reily's nobody had ever heard of an issue like this and was stumped.
I managed to grab a video, excuse the filthy engine bay and the fact I couldn't find the throttle body cables haha.
Uploading video, will be posted momentarily....
Anyone have any ideas?
edit : oh and it has 116,xxx....just had an oil change (was present before oil change)