I installed a 160 degree stat in my car, about 2 weeks later the SES light came on; Scan tool was plugged in and the code read was soemthing about engine undertemp; I have the 194 degree stat in there now and I NEED to put something in, so either a. I will put the 160 in and keep a scan tool handy to reset, or b. just go with the 180 (like everyone else is suggesting)
ON ANOTHER NOTE!!!
A friend of mine has a GMC 1500 Truck, he is going to "upgrade" his PCM by using a handheld tool that makes modifications to the computer.
This thing connects to the car makes changes; you can always undo those changes to. You can also optimize the engine for 87 or 92/93 octane. They don't have one for the 2002 Bonneville (which is what I have) but a sales rep said he would have one after the first of the year, for about $435