From what I've compiled on another forum, the big ticket items for helping these motors are:
-New injectors: If you want your engine reliable you'll want to start here. This should help your fuel economy a little and prevent you from having a failure to start when hot. If you go much bigger than 21lbm/hr (@ 3bar) or 24lbm (@4bar) you'll need to have your ECM tuned. Factory flow rate is somewhere around 22lbm @ 4bar
Factory flow rate injectors (but are 19lbm@3bar), 4-hole nozzle: 0280150556, FOTE-D5B (5-0 motorsports sells these on Ebay and they are what I have)
-Headers and exhaust: Banks used to sell a full tri-Y kit for our trucks, now you can only find stuff used or for RV's. I have Gibson shorties on mine. (The fit out of the box is not right, you will have to grind some of the header flange off to clear a couple of head bolts. You will also need your exhaust adapted to it as their pre-bent pipes do not fit correctly.
Headers and opened exhaust really make a big difference with this motor, and have been totally worth it in my opinion.
-Whipple supercharger: Whipple made a supercharger kit for our trucks. Now you can only find them used, but the supercharger can still be rebuilt. 88GMCtruck has done this and has had his charger rebuilt.
-Cams: From what I can find a 502ZZ cam is a direct swap into our motors, with the exception of needing a new timing set to properly set the cam. Our cams are 12* retarded from the factory... they're ****. There are plenty of other cams out there as well.
-Rocker arms: There is an set of rockers out there that are made by Comp, but if I remember right they will not fit without spacing the valve covers or the plenum. You'll need to get self-aligning rocker arms.
-Tuning and such as: Do a 0411 swap and you can have a local tuner work on it. It would be the same as if they were tuning an 01-02 camaro at that point. If you do the swap you will have to do a Crank relearn. Tell the dealer to do it like it is an '02 Express van with an 8.1 and you'll be fine. With this upgrade you also have "towing mode" and if you swap your shifter out with one from an 01-02 Astro van, then wire it to the ECU (and ground) you'll be golden. A shifter from a newer truck can also be modified to fit.
There are aftermarket tunes for the black boxes. That is an easy forum search away to find.
-Intake: If you feel like you need to, there are cold air intakes available for these trucks, but you already have the HD intake box and "snorkel" behind the fender to scoop up cold air. If you're doing this you're scraping the bottom of the barrel for HP. Then again... HP is HP.
I am not aware of any programmers for the black box that actually add any performance, I also do not know if there are any programmers that would play with a 0411 and our engine combo.
A 28lb injector swap and a dyno tune are in my future. If I get those done I'll be sure to post results.