Vac line is cheap. Very cheap.

I had some issues in my 1995 E300d with my lines, and so I just bought a roll of both sizes (not sure if they are same for your car) and printed a vacuum diagram.

Start at one end, and replace them all.

Newer vacuum lines, combined with older vacuum lines will just lead to more problems.

It was a 3 hr project, and cost me about $30.

it will also give you the ancillary benefit of knowing for SURE that your lines aren't the issue, and you can more easily pinpoint and solve future problems.