Geeze I just changed the fuel filter and had to figured this all out on the weekend. I wish I had seen this post about the M54 not making use of manifold vacuum on the fuel pressure reg. I first assumed that someone had previuosly connected the hose wrong since mine had body work done on that side! I couldn't understand it because it looked factory but didn't make sense. I guess they didn't want to vent the regulator underneath the car and also make use of the same filter fittings/lines. Good to know for sure!
