Quote Originally Posted by mcung13 View Post
I had similar problem myself just few weeks ago on e39. Bank 1 and bank 2 running lean. Lower intake boot had big crack in the part that goes to idle control valve.
mate i think you have hit the nail on the head... did a lot of looking about online and seems massively common regarding the lower intake boot with cracks

i left the car running last night and listened down by the dipstick and sure enough theres a pretty audible sucking noise so i reckon thats the culprit... will be stripping it friday id say