DIY - Volkswagen Tiguan engine code P0507 & whistling noise - issue solved

Investigating whistling noise , rough idling and P0507. Engine rough idling and whistling noise came from PCV (oil separator) module. I bought an aftermarket part, installed and there is an improvement but did not address p0507 engine code. There is huge suction under oil cap and engine oil dipstick. When remove anyone of them, engine will stall. Engine random misfired code P0300 will appear. I am a bit confused as I can’t see anything else could cause same error as PCV module . Perhaps aftermarket part is defective? I ‘ve checked all connection and PCV mounting hardwares . All secured . I bought OEM part to see if that will solve the problem . It didn’t. I try to buy o-ring from dealer but they only sell a complete hose with O-ring. I bought a kit of various O-rings and match the size I need and replaced two O-ring. One from back hose off the Turbo and one from the hose that connect from PCV to intake manifold. That solved the problem. So in summary: PCV module is bad caused whistling noise and rough idling . Also the cause for engine P0507 code. Can’t Aftermarket PCV module fine. The issue is O-ring that is leaking Update: sept 23rd. I re-installed the aftermarket PCV on 2013 Tiguan (same part I removed when I swapped with OEM part I saved ) it works for about 1 day but still not run properly. No engine code but engine is feeling stalling when the car is stop. I replaced with OEM part and the problem is solved . There is an issue with aftermarket part. I don’t...