in the circle is your eng breather hose,the arrow points to the bov... if the breather hose comes loose it will make the spool noise louder but prob not too much as the hole is soo small,and youd notice a little bit of oil spray in the general area.. did you just have the car serviced? if so id go with the theory that its just coz you got a new air filter.. Gypo-that's a dame clean eng bay mate,good to see some people are fussy about their car like I am with mine..