One thing I use the temp gauge for is this.
I normally tune by smoke and response and sond and all that.
When you have your tune just right you can measure the temp to get a base line. Next time you tune and get a good one you can do it again and you will soon have som kind of understanding what your engine likes temp wise.
Then you can use that when it is staring to mess with you. Next time you get an airleak you can use the temp gun and see if the temp is off.
Don't TUNE by it, use it as complement!