Black Bear Performance dot com
I have no idea why, but this site won't let me link directly to them or even type out their full web address. Cuts off the first two words.
You can order from there. You have the option of either sending your PCM in for tuning or exchanging it with a refundable core charge. I actually bought a second PCM from them and had that tuned so I would always have my factory original one to swap in if I ever wanted to. Keep in mind that if you do what I did or exchange your PCM for a different one, you'll probably need to have a CASE relearn procedure done to prevent your check engine light from staying on. The only people who can do this are dealerships and other shops with access to very high-end scan tools (GM Tech-2 preferred). It's an easy procedure with the proper equipment and only takes 20 minutes or so, but that's something to be aware of.