hi there have just started to have a problem with my 06 plate 2.5 focus st !! a squeeking noise started the other day when the engine was running and when i switched it off theres a hissing air leak noise !!anyway i noticed that the plastic breather pipe on the front of the engine was split so ive replaced that with a new rubber version !!!aahhhhhh noise still there so ive had another look 2nite and found that there is a massive vacum being created in the motor !! if i remove the oil fill cap or the breather the vacum is released and the noise goes away !! i just wonderd if anyone eles has come across this could it be the pcv playing up help please