I ran a drilled 160 in my car for many months and never had an SES light come on and it would usually always stay around 160 with a few flicks of the fans (manually controlled). If you're looking to change t-stat expect to make it a $55 investment. $12 or so for the t-stat and about $40 for the adjustable fan relay. You don't need to be so drastic as to reprogram your computer you just need a temperature adjustable relay for the fans. This can be picked up from plenty of quality performance parts dealers. Summitracing.com has a few to choose from like this one from Derale: http://store.summitracing.com/partde...rt=DER%2D16759
Pick one of those up, feed it some juice from the battery, hook the fans to it, and plug the probe into your radiator and you're all set up. Its adjustable from 150deg to 240 and you can set the on-off difference. So if you're running a 180 t-stat you should have your fans come on around 195 and back off at like 180 and that'll keep your engine running nice and cool. There is, however, a little debate on the benefits of this modification. A few mechanics I've talked to don't like the idea because of the generation of water vapors (a natural byproduct of comustion) that gets into and contaminates your oil. If not boiled off by the usual 200degree+ operating temps of your car they could make your oil acidic and begin to actually eat your bearings away. But on the other hand if your car is supercharged this cooler temperature change will allow your computer to put maximum spark advance for more power. On N/A engines it is thought that the hotter the engine runs (without detonation) the more effecient it becomes. I'm not sure if the effeciency is in terms of lower emissions or more power produced per lb of air/fuel. But lets think about this. So one of the goals most people want to achieve is an open loop situation. In other words that extra fuel added during warmup phases of the engine. But if this were achieved that would mean that the o2 sensor would continue to be ignored and proper a/f ratios would not be achieved resulting in poor performance. During open loop the computer runs off a map, much like during WOT. It has pre-programmed spark timing and fuel injector pulse. Thats why there are lots of rough idle problems that go away once the engine has time to warm up. Thats all because a sensor that the PCM is ignoring has something important to say. If there isn't optimum a/f ratios going on how could you expect a gain in performance. Now some people could debate that if the PCM does stay in open loop and add more fuel a good flowing CAI could make up the difference. Technically I would think is possible but not probable. You're trying to do exact science with a t-stat and k&n filter. If an engine is off in its a/f ratio but only a couple percentages all performance gain could be lost, or even reversed. One thing I've noticed that I haven't seen a performance modification about is the battery voltage. Your comptuer reads this almost constantly and will actually add more fuel if it notices a major drain on the battery. Ever notice your rpms go up when the fans come on? I'm curious to see if something can be done with this without adversely affecting your igntion. So I guess the debate will continue until we get a GM engineer on here to explain all this to us. For now I would read what you can about the modification and if you're going to do it, do it right and get a relay for it.