If you order your gauges from Geno's, they come with instructions that used to be posted on TST's website. WHATEVER YOU DO, READ THE INSTRUCTIONS FIRST!!!!! Being the "seasoned" mechanic, I looked at the exhaust manifold and decided the middle would be the best place to install the pyro probe. I found, much to my dismay, that the manifold is divided.
If you need more specific directions on where to drill, let me know. I kept my instructions from Geno's