I bought a used 2013 z71 about a year ago, it had 20k miles on it when I bought it. I'm not sure what all has been done to it other than the factory muffler being swapped out with a flowmaster, and I'm assuming it's had a programmer hooked up to it at some point. I assume that it's had a programmer hooked up since it has a 295/75 tire on it but the speedo is still reads correctly, and it also never kicks down to 4 cylinders when cruising.

The truck shifts VERY hard, if I get on it, it will break the tires loose going into second and if the roads are wet it will break them loose again going into third. If I'm cruising down the road and get on it, when it down shifts it will slam hard into gear, almost like the trans starts to slip a little, but that's the only time that does that, just when it kicks down a gear.

I have a Superchips programmer, but its VIN locked to another truck, before I spend the $100 to get it unlocked I wanted to get some opinions on whether it would be worth it or not to hook it up to the truck, I don't want to end up messing up a tune or anything that may have been put on the truck previously.

 

I also forgot to mention that anytime it idles for a long period of time, say 10 minutes or so sometimes less, it will kick out P0171 and P0174 lean condition codes.

 

Take truck to dealer reflash to full stock tune. Take truck to tuner get a custom tune done. Don't waste your money on hand held diy tuners complete trash.