does the Edge Juice w/ Attitude improve mileage or is it just for power? why the CTS guages 6x6in6?
As with any any power adder, it's all about the driver and how heavy your foot is. Under normal driving conditions you should see a 10% ish fuel economy increase. You'll likely never pay for the purchase of the J/A in the life of the truck in fuel economy if that's what you were wondering.
I assumed you did not have gauges currently installed, correct?
If not, and having a VP injection pump engine, you should get the accessories needed to monitor your fuel pressure, egt's and transmission temp at the minimum. Turbo boost is another one you should consider. The boost is good and also helps diagnose that a boost leak exists like intercooler boots, intake gaskets, pretty much anything on the charge air side. If you tow heavy, you can get the rear differential temp sensor. There's other things to monitor too if you choose too that utilize sensors an not reading off the ECM, like oil pressure, oil temp just name two.
I have mechanical gauges in my '05 and a CTS in my '07. I like the mechanical better for a quick glance read while driving but I like that I can I read 12 or so different readings on the CTS.