[Schulisco]

Check the mixture with a Lambda tool over the whole rev band. Mine (930/16 with lambda control unit) was laggy too over 4000 rpm. It was way too lean. I figured it out without a Lambda tool while bridging the csv manually via switch on the dash when I revved it over 4000rpm. So I found out that it was too lean and checked and adjusted the sensor plate height and have the fuel distributor and the wur overhauled.
The recent discussion in another thread here by having the csv controlled by micro switch on the throttle is not necessary when the CIS works as designed.

Also check for vacuum leaks. They can also make the engine running lean. But such huge vacuum leaks influences the idle and cruise as well...how does the car starts?

Thomas