380SL with 560 SEL engine

I recently purchased a '82 380SL in great cosmetic shape. The problem is it has '86 560SEL engine and trans. which performs well except for the idle speed. It idles between 1000 and 1200 rpms.
Have checked for vaccum leaks and found none. Have checked air slide valve and it checks operating. Linkage is okay. It still has the 380 idle control unit which I now believe that this must be the problem. Previous owner says that car never idled right after change of engine. The problem that I see in changing this is that the connection to the 560 idle control is different to the 380. Any help or suggestions to help solve this will be greatly appreciated.

Thanks in advance,
Rayson

[stevebfl]

The two engines used very different engine management systems. We did that install on a car years ago and had no problems (actually it was a 500 into a 380). I am pretty sure we used all the 380SL management system.

What kind of fuel dist is it? Is it a KE with EHA or a K-jetw/Lambda using a frequency valve?

I think you would be best suited to finish the system that is working with the fuel dist as the controllers have to work together.