running hot

My 96' Cutlass is running hot. This started with an intake manifold leak. We had that replaced and since then the temp. gauge raises quite high while in traffic or at a long light. I can tell when the fan turns on because something must be wrong with it.... it vibrates the entire car. The fan does keep the car from overheating but it seems that only 1 fan is running. Are they on seperate thermostats? Could one be dead? Should we be able to watch the gauge go up and down when we are driving in stop and go traffic? It didn't used to do this... nor did my other 96' Cutlass. I've returned to the shop that replaced the intake manifold seals because it was still running so hot. After two return visits they told me they had to reset the gauges and collobrate them with the computer. This sounds bogus to me.... especially since it still gets on hot in traffic.... the only difference is the guage now starts well below zero and doesn't really go much higher than 3/4. Very annoying that this guage doesn't have #'s on it. Any thoughts?

Sounds bogus to me as well. You can reset the computer by removing the negative cable on your battery or there is a fuse on the fuse panel that can be removed to take power off of the computer.
I replaced those gaskets myself and have not had an overheating problem or a problem with the temperature fluxuating at a stop light. Not to overlook the obvious, but do you have sufficient coolant in the system? There could be air in the system that uncovers the sensors and gives you incorrect readings on temperature. Just some thoughts.