YEsterday I did it on my 93 325is so its m50. I didnt take of the intake manifold (would have made the job alot easier) but is about in directly underneath the middle of the intake manifold. about the size of a of a 6oz bottle with two connectors coming off eachside of the top. Here is a picture from this site along with the thread its from.
but that is for an m50 I have yet to find one for a m52 but i imagine they are similar