Clogged Cat And Operating Temperature

I was just wondering if my clogged cat could be responsible for a
10-15 degree increase in the operating temp of my 380sl, given that
the thermostat, radiator, fan clutch, water pump, and temp sensor seem
to be operating correctly. Tthe car operates between 80 and 90 when
I'm on the highway, but the operating temp is now rising  quickly when
I'm in traffic or stopped at a light -- which it never did before. 

Thanks in advance