I just swapped out my vacuum pump. It is really very easy. I turned the crank to the BDC as Pierburg recommends. The basket was already removed or not orginally installed and I just used the dam gasket. When I removed the old VP, I noticed some scoring on the cam of the IP timer. I went ahead and installed the new one but ordered a new timer. When ready to install the new timer, I re-examined the cam and it was very smooth. The only thing I could think, was that the the VP cleaned up the cam by slightly burnishing in the 2 weeks of driving. I can't return the timer since it came from Mercedes so does anyone need a timer for a 603? O.