This is what actually started me on doing all the minor engine repairs on my 124. I had #4 start leaking a few months ago and I replaced the line. This time #1 was leaking on my way to work so I ordered the other 5 lines ($22 each) and planned on replacing them that weekend.
I pulled the intake manifold since I needed to replace the gasket anyways and figured since I was this far, I might as well fix that exhaust leak in the flex piece. Most of you know what happened next, my issue with the exhaust stud
So the moral of the story is, leaking fuel lines are the direct cause of broken off exhaust studs
