You are getting to that classic point of having almost all of the bolts ons and still wanting more.
The TB is a good option as well as a dyno tune to be sure all of your parts are working together. A tuner can do much better work hands on with your truck.
If you want to stay NA and make gains you are going to have to go into the motor. Headwork and cams are a good option, but if you are going to pull the motor you might as well go ALL out with new rods and pistons while you are at it. The labor to pull the motor is up there so you only want to do it once.
If you do a built motor think of your next step after that though. If you think, even think you might want a SC or turbo later plan for that now so you don't have rebuild the motor later.