How much are you willing to spend?
I'm running JLT with tune also, with catted x-pipe, Bassani face mufflers. These helped me gain some power but all us running the same mods have HP flatten out around 5k generally from looking at dyno results. TQ usually stops building aound 4.5k and dops off.
Everyone gains a noticeable amount of acceleration and grunt with gears. Supposedly cams with headers will help breathe up top which is what you're asking about. I'm getting headers and calling it good for now.
All these mods to improve mid to top end total around the same cost a Vortech supercharger that can be upgraded as the engine/trans are. I'd go that route if I had the time to invest in the car.