My 300CE puffs out some smoke from the engine breather hose. Also some oil deposits inside the air filter cover. Is this normal for a M103 motor? I get an occasional misfire and one wet-oily (engine oil) spark plug is usually the cause of the problem.

One MB service technicians say it needs new piston rings. The other says a valve job would suffice. A Compression Test was performed and within Mercedes specifications.

I have changed the following in the past 6 months:

Ignition Sender Unit
Ignition Coil
Ignition Distributor
Ignition Distributor Cap
Vibration Absorber / Balancer
V-Belt
Fuel Pump Accumulator
Fuel Pumps x 2
Fuel Filter
Fuel Injector Nozzle / Seals
Fuel System Valve

I have not replaced the Ignition Cables. Could this be possibly the cause?

Otherwise, the car runs very smoothly, no oil/smoke from the exhaust. What gives?