revs dropping down very slow after A/C compressor replacement

[Ulrich]

S60 2001 , non turbo manual transmission

Hello,

i have a problem since i replaced my A/C compressor (including dryer, both lines and the pressure switch).

During gear shifting, when A/C is turned on, the revs are staying at around 3000rpm for about 3 sec. before they getting down to 800 rpm.
The idle is very stable an good, no matter if the a/c is turned on or off.

Also the revs are going down a little bit slower during shifting when the A/C is turned off, which was not the case before the replacement.

i replaced many, many parts which i can exclude , i think .... MAF sensor, pcv system , all gaskets for the intake ( also no vacuum leak), oxygen sensor, for sure a good ECM (overhauled)... a lot more / as i said the car was working (nearly) perfectly before the A/C replacement.

i have measured the A/C pressure (with a obd tester) it is about 1050-1600 kpa.... when a/c is on.

does anyone have any idea , or facing the same issue?? ...bad compressor???