2005, 93 tid 150 when I rev the car specially with the bonnet up I can hear a quite loud air leak sound, can't quite work out if it's a boost leak sound or intake/suction sound I've previously quickly checked hoses and all seemed to be ok ,car seems to boost ok apart from a brief blip in on wot , just wondering if someone with same car/engine has noticed how loud theirs is , my bro has got an astra cdti 150 (same engine) and his boost sound is really quiet compared to mine