I don't know your car, but I did a search on "vacuum modulator removal" and there is a thread in the diesel group about a little plate that holds it in. In that case, you need to remove the holding plate (easy on the allen bolts) and then the unit pulls straight out. This seems to be the set-up of the 722.3 and 722.4 transmissions.
If your trans. is different, somebody will hopefully point out.