I certainly hope someone out there can help me with this one. I have an 87 300SDL (OM603) with 250K. Since cool (not really cold) weather started happening, I get no (zero on a gauge) boost pressure for one to three miles driving then suddenly and I mean suddenly within a second or two I get boost and all is well. First thought was a protection valve or some electronic thing, BUT... I have hooked a gauge directly to the manifold, disconnected the line running to the ALDA, and it still does it. All the vacuum stuff, EGR etc on the right side of the engine has been disconnected for over a year since I put on a new head. I jammed the waste gate closed with no effect. Of course with the ALDA disconnected I only get a small amount of power increase when the boost comes on, but I do still get boost. What can make the pressure build so suddenly? There is a vacuum operated valve on the turbo itself that has always been disconnected since I got the car. Could this have something to do with it?