There are a few options for you.
1. Go to a place that takes your setup information, and "custom" makes a plug-in chip for your PCM. This isn't the best way to go, especially since every car is different, and it's guesswork at best.
2. Buy something like a twEECer.
Click here for more info on that. There are many other systems available, but that one's my favorite ('cause I'm a geek
). They allow you to custom tune and tweak your mappings to your liking. However, you can really do some damage to your car as well.
3. This is the best method: take it to someone that can custom burn you a chip. Such a tuner should use datalogging and a dynamometer so that the chip is truly doing you good.
Of course, all of this depends upon how far your modifications have gone. What's your combo???