I've been getting a check engine light with a P1492 code (Downstream Throttle Air Leak) on my 2007 Mini Cooper S (R56 with N14 engine). I can clear the code but it comes back about a week later. There is a hissing sound coming from the left rear side (on the left when facing the engine, it's on the right side of the car from the driver's position) of the cylinder head cover after I shut the engine off. The hissing lasts for about 20 seconds and as it slows down, it "burps" and goes for another couple of seconds before stopping. The car is not running as well as it used to. I'm assuming this hissing sound is not "normal". I took the cylinder head cover off but could not see anything apparent but I really didn't know what I was looking for. The hissing seems to come from the back side of the cover next to a hose that connects on that back corner about in the center of the photo I've attached. I wanted to check with the experts on the forum before I spring $300 for a new cylinder head cover - is there anything that can be done to fix the cover or is replacement my only option? Thanks for any advice.