P38 2.5 DT sucking noise

Hi Guys. Great site. I have an issue with my R Reg P38 2.5 DT strght 6 BMW auto. When box accelerates through all gears at the top end of revs in each gear there is an air sucking noise that comes from the engine on the drivers side. Also my MPG has started to slowly reduce over the past couple of weeks. Reading on dashboard has gone from 23 to 22.9 to 22.8 to 22.7 etc. Air suspension is fine. No oil in water, no fuel leaks ...and yes I have been driving with all windows shut. Is this a problem with air intake through hoses on turbo/air filter etc . Thanks for any advice offered. RoverRat

It sounds like you have an air leak. Check all the hoses and pipes between the turbo and and the inlet manifold. Its probably blowing out as apposed to sucking. Are you loosing a little power too?