Mercedes: 1971 Mercedes 250, dual pipes, mercedes 250

Question
I have a 1971 Mercedes 250 that has a hesitation when taking off, I can't seem to get rid of.  Fuel pump was replaced along with filter and lines cleaned.  Gas tank was removed and reconditioned. New plugs and wires, I also use a premium fuel.  Service records from previous owner indicates past history of this, but Mercedes Dealership never found problem.  This car was serviced by an authorized Mercedes Dealer. I did switch to a single exhaust but hesitation was present with dual pipes.  What do I check next?

Answer
Steve,
It sounds like a broken timing advance. Or a vacuum leak on the advance diaphragm. Find an independent shop that has a sun diagnostic machine with scope or equivalent.
If the vehicle has catalytic converter it may be clogged. This would not allow full acceleration.
Good Luck
Rob