The old vortec 350's were just better...in stock form. New ones respond better to mods and there are alot more mods for these newer ones then the old ones. Torque numbers are about the same on them but the 5.3's reach their peak at 4000rpms(way to high for a truck motor) the old 350's were ~2500rpm's if I remember correctly.

I had a '97 with a 350 until I traded it in for my current truck. With just a drop in K&N and dual flowmasters it didn't have any problems beating the '99-02's with similar mods off the line or on the freeway. And for some strange reason it started getting 20mpg after I passed 80k miles in it.

Kind of wish they still had the old vortec 350. I know the guys that just want to mod and go fast love these new ones, but they suck for pulling stuff compared to the 350.

 

before you go out and gut your cats take out the front o2 sensors and drive the truck if its the cats this should free up the exhaust just to test it out
also it could be low fuel pressure

 

Well im no expert but if yu have stock tune yu can relax,Because its called torqe managment.Get one of allen tunes pull 80% of tm out and yu will be sideways in no time.

 

There's no such thing as a free lunch. If you want zero risk of breaking things then stay stock and drive like grandpa. Otherwise, if you really do want more low-end, you're going to have to take a few risks. These risks, however, can be mitigated with a little more work and some intelligence.

If you want low end, get a Radix. It really is that simple. Couple it with a cam like the one I have in my sig, and you'll have more low-end than you know what to do with. Get a shift kit/servos for your tranny and an Eaton for the rear and you're set for some fun - some fun that should last for a while unless you get silly with it.