On the turbo engines with more oil running hotter I think the oil cooler is needed...
However, my 300D had the same issue. I bypassed the oil cooler fully, and machined a threaded piece of metal line to connect the two ends together...
I WOULD NOT use clamps and hose...the pressure is very high, and I had a bad experience were a line burst through the clamps and shot oil all over my engine bay. Thank the Lord that I shut it down VERY quickly.
I've read posts that the NA engines never came with oil coolers in Europe, only the ones sent to do livery service in hot climates received them. IMO, on the NA engines, it isn't necessary to have the oil cooler. On a Turbo engine, I have no idea.
All I know is don't use clamps. Thread a piece of pipe so that the metal ends of the OC lines can screw on. Apply loctite, and it should be set. Mine has been working for 1 year, no issues
