86 300 SEL (Euro) cold idle stalls

I have an 86 300 SEL EURO that I bought new in Europe. It was converted to US standards.
About 10 years ago it started stalling at cold idle. It runs ok when emissions is increased, but runs rough and stalls at emissions standards. Injectors, fuel distributers, idle control modules, and cat changed, but still stalls at idle. Runs ok when hot. Also,it sometimes oscillates (RPM) and makes a clicking sound before it shuts off. Any ideas.

Thanks

J D