2005 impala heating up

alright lately since i drove down from michigan to florida my car is running a bit warmer than usual. i had the intake gasket replaced before i had left michigan. now it is running up near 200 during idle, or stop and go. as soon as im driving it cools back down near normal level. i had a friend who told me it may be the thermestat is sticking. i had a cooling system check done at the dealership. everything appeared to be fine. anyone have any ideas what it could be? also, i know i may need a new cat if that would have anything to do with it. oh and one more question. would it mess up my air flow sensors if i hollowed out my cat or put on a straight pipe? its a 2005 3.4

The standard thermostat opens at 195 degrees... So it sounds normal to me...

It could be ur coolant mixture. We adjust our antifreeze mixture for our retarded climate in Michigan. Like -20 to 100 degrees. You might need to make a simple adjustment for warmer weather. Not sure on the %, just a thought. Elevation will also effect a vehicles performance. So if ur in the mountains ur car needs to be re-tuned for that elevation.

I cut the cat off my 95 3.1 and put on a straight pipe to compensate my port job on the heads. Seeing that u have a 2005, u probably have a billion more sensors than I do so im not too sure about it. But I would do it if I needed to do it, not just for the hell of it.