I hear a vacuuming noise coming from the boxster

[polkfarmboy]

I heard this the other day but thought some one was vacuuming there car in the next garage. Well I went out for a new bulb today and left the car running after I pulled into the garage and vrrrmmmmmm there it was coming from the front passenger side.

There is no code showing up at the moment so any idea's whats going on? I should mention that the car is running lean and I smell a rich mixture of gass from the exhaust. Ontop of that I had a error code that cleared relating to the evap emission sensor.