Bringing alive an older post
Been down due to the offseason (home renovations)
I'm using HPTuners. It's really good software and the scanner is top notch. Great with a wideband too (just ordered the USB Pro Upgrade!).
If you don't plan on doing the tuning yourself, or just plan to stick on a CAI and exhaust, a PCM swap is probably your best bet (just not as fun).
I think DPP, Milzy, Intense and DHP all sell modified PCM's for the 3400.
As for the 4cyl, HPTuners now has the 2.4