Hi guys I have a 1993 940 Turbo with 61.000 miles and today in traffic my RPM start doing weird going up and down.. What is the problem? The car has the same power but soon as I get to the stop light the rpm goes up and down and the engine is vibrating like is dying

 

sounds like an air leak somewhere between the MAF and the turbo - or possibly the MAF.
Probably has some DTC's you might want to read from your OBD plug