This guy is probably in the same situation i was, not wanting to die when merging onto the interstate.
Your throttle cable loses tension over time, so by now you might be hitting 3/4 throttle when you floor it. Also, you kickdown cable may not be engaging right either. You can lift up on the pedal, and wrap zipties between the pedal assembly and the little ball on the end of the cable to take up the tension.
Theres a big plastic baffle stuck inside your dildo looking air horn from the air box to the throttle body. This thing is supposed to prevent air noise, but I've not noticed any noise since I pressed mine out with my thumbs. I did however notice alotttt more throttle response.
Also, your air horn is big, hard, smooth, and black, and soaks up alot of stagnant heat under the hood because of this. I scuffed mine with a scotch brite cleaning pad and painted it silver to reflect some heat. I don't know if it really helped any.
Your cat converter is probably clogged up. From my experience, these things can become clogged after as little as 30,000 miles. If your in a smog testing state, replace it with one from cherry bomb or such. If not, delete it.
The stock 2" exhaust and stamped steel muffler on these trucks are really restrictive as well. These trucks don't need alot of backpressure. I hate obnoxious 4-cylinders, so I had my stock exhaust replaced from before the cat with a 2 1/4" pipe, that moved up to a 2 1/2" pipe about 2 feet before a stock Expedition/Trailblazer muffler that turned out the side with a 3" slash cut tip. Better throttle response, its not loud or quiet, and is not ricey at all. The SUV mufflers are pretty compact, and always have a heat shield of some sort attached to them to protect the spare tire, which you can use to keep reflect some heat away from your truck. They are usually paired with a resonator or two, and are not very restrictive when used alone.