I'm not so sure about open source options but I've done this before using customized configurations for my '96 Chevy Impala. The PCM was from a '94 and was an ODB1 unit (more programable than the ODBII based PCM), hooking up a laptop with a custom built ODBII to Serial cable I was able to use various shareware / freeware to flash and monitor the PCM. It has been a while so I'm not sure what software was the best. There are a number of people (i.e. http://www.pcmforless.com/ (who I used)) that offer tuning services online because they know what the correct settings are for various vehicle configurations. It is not a good idea for a novice to just jump in and start changing fuel mixture ratios or shift points on the transmission ;)

The time I was in South Korea, this old lady was cooking them up in some kind of syrup. They smelled great. At the time I didnt know what they were but they looked like grubs to me so I didnt get any. Only found out last year that those were silk worm pupae. Guess it is all in the recipe ;)

Oh memories. I still miss vamps =\ The terror of seeing the line of text stating that you've been staked.