GraphiteSilveradoZ71

I came across this feed and something similar in another group. I’m looking to do the same if not similar on my 5.3L 1500. Is this on a 5.3L/6.2L 1500 truck or 6.0L 2500/3500? the black connector coming off of the grey relay, what does that connector go to? I’ve tried looking up the wiring diagram and have had no luck.

I have a ‘17 Silverado 1500 Z71 4wd with the 8spd transmission. I recently purchased 6” lift kit (not installed yet) and currently looking to purchase 35” tires. I’m currently running a 2.75” level and 305/50R20 A/T tires, Carven cat back exhaust, and using a Diablosport intune i3 programer and have had no issues. My question is, will running a tire larger than 33” cause any transmission issues? Anyone have transmission problems running 35’s? I know on the programer i can change the tire size to correct the trucks speedometer.