560SL power loss at high RPM

[Jerry Hudson]

I have seen alot of great advice shared on this forum and I hope someone might have be able to help me on this one. Thanks in advance for any suggestions!

I have a strange problem with my '88 560SL that I need some advice on.

During normal driving (below 4,000 RPM) the engine runs strong and accelerates smoothly. But on occasion (like most of the time) if I really get on it say from 60 mph it will downshift to 2nd and the tac will jump to about 4000 rpm's and it's almost like the timing gets retarded or the fuel flow is reduced and there is a slight vibration coming from the engine. When this happens it will continue to accelerate to redline but at a reduced pace. When it shifts to the next gear and the rev's drop below 4000 rpm's it begins to feel strong again. It's almost like a governor or rev limiter kicks in slightly. I can also cause this to happen if I put it in a lower gear and gradually accellerate past 4000 rpm.

I bought the car about 6 months ago and have already replaced the following:

Sub frame mounts and motor mounts
rear flex disk
both fuel pumps and filter
idle air valve and hoses
new copper spark plugs, rotor, disributer cap, plug wires and air filter
air distributor hoses that connect to the fuel injector's.
timing chain and tensioner

I have also checked for a vaccume leak and ther doesn't seem to be any.

Is it possible that a coil or EHA could cause this????
Any help or suggestions would be greatly appreciated. Thanks in advance...