What to change next for more power

Hello All,
I have the Predator U7192 (latest firmware) installed in my 07 Silverado Classic, extended cab, long box, 4x4, Z71 with heavy duty tow kit. I have a K&N cone filter and cold air intake installed on an otherwise stock and very heavy truck (I have adjusted the injector slope). I am running the 87 octane tune right now but will be taking the truck to Georgia where I can switch to the 91 octane performance tune. (gas is at $1.29/litre for regular up here, $1.39 for premium) I am looking for a recommendation on what mod to do next to get some more daily driving umph. I was thinking some shorty headers (Summit brand)and a cat back exhaust (Flowmaster or Magnaflow single pipe) to bump up the torque, maybe some higher ratio rocker arms, but I am open to your suggestions. A full forced air system is out of the budget but pretty much anything else will be considered. Thank you for the ideas.