Distributor cam lube is used on old distributors that use points and condenser. This would not apply to your 103 motor.
If you paid someone to do the work and you're experiencing degraded performance afterwards, have them review the work and solve the problem.
On a side note, the resistor tip(part of spark plug wire that attaches to spark plug) can be easily damaged on removal. Depending on how often the plugs have been changed, they've been yanked off at least that many times.
It's possible one of the resistors has slight damage. This is but one of many things that could be causing the slight miss.
1991 300-SEL - Model 126
M103 - SOHC
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