I have a 1991 300SEL with ~170000 miles. Recently I have been having a tough time on cold starts. I crank and crank and it just does not catch. After about a minute of cranking, it catches. The first two minutes are rough with the engine really struggling. If I wait a few minutes and then give it some gas, the engine runs well. Once the engine is warm it runs fine. I don't have problems with warm starts.

Things I have done:
Changed fuel injectors
Changed air filter
Fuel filter recently changed
Fuel pump sounds good and changed 15K ago
Oil change

Any ideas??