For the injectors, you may want to remove intake manifold, remove the lines going to them, keep everything clean, you may need a special socket, for my om606 I bought the special socket, but a deep socket of the right size might clear the nipples for the return lines (you don't want to damage them). Also there is a washer (heat shield) that sits between the injector and the head. Make sure it is in the right way. Some have said that the expensive german ones are better. Make sure you torque to proper lb ft. Reattach fuel lines. Check all of your lines to make sure the clips are holding them from rattling against eachother and the engine. I have not replaced all of the injectors before, but have removed one that was leaking compression.

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1990 300d 2.5 turbo
1995 E300d