M54b30 – strange hissing/airflow noise near DISA/intake area
Ever since a recent major service + water pump/thermostat replacement, I’ve been hearing a strange hissing/airflow type noise at idle. It almost sounds like the interior fan is running even when the HVAC is off.
The noise seems to come from around the DISA/intake manifold area (maybe lower down), gets louder when the engine is fully warm, and I can even hear it slightly from inside the cabin while sitting at a stoplight. While driving it’s much less noticeable.
No overheating, no CEL, car drives fine and idle is mostly stable. I also noticed one warm start after a thorough car wash where the RPM briefly went above 2k before settling down normally.
Attached a video where the noise can hopefully be heard.
Any ideas? DISA seal, vacuum leak, intake boot, CCV, or something else?
I’m goingto drive through the Alps for vacation on Monday, so unfortunately I probably won’t be able to do a smoke test until after the trip.