new exhaust

i have a 99 sierra 1500 with the 5.3 l 323. it has 216000 miles but runs like its got 50000. i want to add a performance intake and exhaust just to gain a little more power and better sound. i am trying to gain an outside opinion wether or not i should do this upgrade. any help would be greatly appreciated. thank you  

I built my own custom exhaust from the catalytic converter back on my '06 Chevy. It was definitely a big improvement over the huge bulky restrictive muffler...but I won't sit here and try to tell you it pulls wheelies or runs 10 second quarters!
I cut off the stock exhaust at the straightest point behind the cat and replaced it with a Dynomax turbo(3" inlet, 3" out) with a 3.5" turn down at the rear axle. In the past I would have whacked it all off and ran dual straight pipes with big chrome tips....That's just Redneck as hell!!
My truck has a nice deep rich sound under excelleration, without all the pop and crackle, and smooths out at cruise speed or idle. total cost: less than a hundred bucks plus a new blade in the sawzall. You may want to take a look at replacing your cat with that many miles.