hi Spinx
bear with me now and excuse my english,but i will try and explain what it was on my car.
if you look at air filter housing you should see black air flow tube coming out of it(next to the battery)and connecting into another tube.jubilee clip was missing that connect the two.
i put jubilee clip there.noise is still present but a bit quieter.
i dont know whether is the same thinhg on yours or not.
anyway CJ says is nothing to worry about.
all the best
zoran