Level Kit/Dealer

[JT2000]

I know I know this topic has been beat to death. So I know next to nothing on this subject. On another thread I posted a rep from RC said with their 2” AT4 level kit you do not need new UCAs. 
 

So with all the options and confusion I called my dealer where I bought my truck. I talked to the service manager and he said he hated the RC lift for the AT4. He said though instead he used the level kit from RC for the regular trucks and shaved it down and put it on a certain way. He said he is happy with everything this way and if something goes wrong I’m covered there. 
 

He also told me not to put any cold air intakes in. He said GM won’t even sale me one unless I got it with the truck. He said they are burning to lean and messing up the pistons. He said that’s what the flashing was for to fix this. I wanted the S & B, but now I’m torn.