I already had 8.3 running on my box. PT3 installed 8.4 and managed to nuke my configuration and now a ton of my command-line tools don't work. That's pretty sloppy work. Please create an installer that knows how to play nice. Hint: instead of just looking at /Library/xxxx to see if one is installed, which is what I presume you did, why not check the ports on the localhost to see if a database server is listening? Especially on Macs, there are lots of alternative ways to install things. In my case, for example, my pg was installed in /opt
At first I thought 8.4 would be required but that does not appear to be the case.