There is a guy in Topeka that lives and breathes the Gen III and Gen Iv motors. He did a tune on my 2011 SCSB 5.3 and it was worth the effort. I believe that he could help you out if you desire it. He does travel around some and gets down to Wichita quite often. Send him an E-mail at
AkNovaMan@Gmail.com. His name is Anthony and is pretty friendly. This would be a tune and not a programmer. He can also adjust the shift points on that automatic, to get rid of the flareout effect between gears. His tunes are around $175.00 and if you need more assistance he will help without a lot of bull.
You didn't say what size tires you are running with that 4.8. My truck came with some pretty tall tires for it's factory rims.