I changed valve cover gaskets on my 1991 560SEL the other day and now the car runs poorly. Idle seems ok but acceleration is very rough.

I'm wondering if one of two things I did may have caused this. First, I had to disconnect the two fuel lines that pass over the valve cover, the main line and the one going to the pressure regulator.

Second, the vacuum line going from the pressure regulator to the valve cover breather hose broke some time ago. I had plugged the opening on the breather hose to prevent oily gas from discharging but I never did anything with the the end coming from the pressure regulator. While replacing the valve cover gaskets I decided to plug that too.

Is there any reason either of these things could cause sudden poor performance? I did check all of the spark plug wires and they seem ok.

Of course, I don't expect a diagnosis and I'm no mechanic, I'm just wondering if there are any common issues here.