I have a 1972 350SL with 3.5 liter engine and it won't rev above 4000 - 4,500 RPM. I've checked all the usual things and replaced points, plugs, set the valves, checked the timing chain, and adjusted the throttle linkage. Spark plugs look normal. Fuel pressure stays right at 30 PSI and ignition distributor is advancing fully. Looks like it has new trigger points and maybe a new throttle position switch. Engine pulls OK up to about 4,000 RPM and then it just stays there and won't go much higher. I'm getting 40 degrees of timing advance so it shouldn't be a problem with that. Seems to be missing at higher speeds and then it goes flat.

Any ideas would be helpful.