Those pressures sound OK. If the sight glass is clear and the system is cooling well, don't touch it!
If you are having system problems with compressor not operating properly, I would build a bypass relay to bypass the speed sensor on the rear of the compressor. It was only there as a precaution and now Mercede has done away with most of them.
You will need a 4 pin relay rated at 30 amps and an Electrical Manual. We sell them on CD if needed.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS