My 75 SL has a 4.5L from a 71/72 300SEL (117.982). It has D-Jetronic FI, and from what I've read this system is entirely vacuum dependent for it to work right. I have a big intermittent miss (more like a near total shutdown @70-80% power loss). Going to replace fuel pump, but also want to install new vacuum lines. Here's the question, I've seen this stuff in bulk and need to know if there are multiple sizes I need to have, or if there's one standard size when I start untangling this maze. There appear to be more than one size, but I have no idea which lines have already been replaced at one time or another. Also, do I need to be looking at replacing ALL vacuum lines. These things run from one end of the car to the other! Or, do I just need to concentrate on the FI related ones? Any suggestions/comments from anyone who has tackled this are appreciated.