Chevrolet: 96 Corvette overheating., coolant tank, k n filters

Question
My wife just purchased a 1996 LT1 Corvette Convertible 350 cubic in. 300 hp.  Yesterday while driving the engine temp was about 210.  When she stopped at a light the engine temp went to red line( above 260).  Once she started moving the temp went back down.  She took the car to the dealship, and they told here that the car was not over heating.  I not sure how they determined this.  They told her that the coolant tank and the overflow tank were okay.  The belt did not come off the car. THe water pump was working and the two cooling fans were working. THey don't know what the problem is.  THey are suggesting that the K & N Filter system that is on the car could be causing the problem.  There is a sensor inside the air intake that if it gets oil on it, it will quite working. I don't know what to think of that. I have never had any problems with any K & N filters that I have switched to.  Could the Dealership be blowing smoke?  They don't know how long it will take to fix and are not sure of what the problem is.  They do know that the car is not over heating and it is not the gage.

Help.
Thanks

Jim

Answer
JIM, I think that they are full of it, as I would flush the system out real good and than replace the thermastadt with a 180 degree size and add a can of coolent with the antifreeze and make shure all hoses and clamps are tight etc. that should do the trick. as far as a K&N ???>??dont know what that even is, also make shure the belts are tight also. as you should run at 180 temp no higher than 190 or there is somethinbg wrong and if you have air cond it might run a bit higher but no way over 195/ 200 as that is hot for a small block good luck
ps
sorry to take so long but there was something wrong with the e-mail ok