I had noticed my car to surge under heavy acceleration only when the engine is cold. Once it heats up, it runs great. It used to stumble on hard acceleration all the time just like your symptoms. I changed the plugs, distributor cap, and rotor with a fuel injector cleaner in a full tank of gas once a month and now it drives like a charm.

Sometimes the simplest solution is the key to most of our problems.

Bernie
1986 190E 2.3-16