Today I noticed a new sound coming from the engine compartment. I'm stopped at a light and I can hear a faint clicking noise coming from the engine compartment. When I got home I leave the X running, put the transmission in drive, apply the parking brake and open the hood; as I soon find out the clicking can only be heard when the car is stopped and either in drive or reverse. With the hood open, I put my ear next to the region of which I can now pinpoint the origin of the clicking noise. I think it is the "EVAP canister purge valve unit" emitting the clicking noise. It is directly to the front-right and top of the engine, almost right behind the MAP sensor. Does anyone know if there is something now wrong with it? Or has someone heard of this issue before? I have 18000 miles on my X. Thanks.