I got my car tuned with the stock stat, but they said that that they would tune it as if I had the 160 on. I bought the 160 at MTI that day. So when I put the 160 on, it still ran the same temps. What's wrong?

 

Are you going by a scanner reading or what your stock temperature guage is showing? On '99 and up F-bodies the temp guage is notoriously innacurate. It's like an idiot light. It kinda moves once to show you're warmed up, and once again to show if you're overheating. It can't be relied on to show whether your coolant is running at say 175 degrees vs. 210 degrees.
Just like you, when I went to a 160 tstat and reprogrammed, the guage showed no difference. ATAP and you will see the difference.

 

It's not the Thermostat, it's the gauge. There are lots of threads out there about this. 99+ F-body owners basically complain that the gauge is nothing more than an idiot light with a needle, becuase it just sits there on 210 degrees and doesn't move unless the car's not warmed up, or is actually overheating.

Check out this thread over on ls1.com, it addresses exactly what you're asking. http://www.ls1.com/forums/showthread...hreadid=236471

 

Thanks for the info.

 

On my car, the gauge will read the same (a little less that 210) even if the real temp is anywhere from 175-240. Plus you won't notice that much of a difference with a new thermo, although it does help!

 

Ditto.You need a diagnostic scanner to monitor temps.

 

It also wont do you any good unless you change the fan settings.

 

I'm sure that was part of the tune.