Just above the throttle body, IIRC. Take the plastic cover off the top of the motor, you can take the rubber strap off from around the ICV, unplug it, remove it and clean it with carb cleaner, brake cleaner, etc. When you are finished it should be really clean and as you roll it, you will hear that cylinder with the funny slot cut in it rolling around inside. You can see that in the opening.
Mine was filthy at 90k mi. Also make sure your fresh air hose doesn't have any cracks in it and the seals where it meets the throttle body are tight.
If that doesn't fix it, it's probably the PCV plate or intake seals, etc. I redid all mine at 100k, and cleaned the intake, did the galley cover, water pipes, etc. etc. etc.
She purrs like a kitten and has good compression and leak down!! 110k on the Nik Block!!!!!
Robert Callaway
Dallas, TX
'94 530im 143k mi
'94 Land Cruiser FZJ-80 202k mi.
"If I could have back all the time and money I ever spent on cars.......I'd spend it all on cars."