How do I find where an environmental variable got set?
~/.MacOSX/environment.plist is read at session start. If you want your change to it to be tested immediatly you have to restart your session.
A restart of the system is useless.
You can edit this environment initialisation file with:

plutil -convert xml1 environment.plist
vi environment.plist


I advise you to simply recover it to its version prior to your software
installation.

Other hint, check all the files which were modified on the date
of installation of your unwanted software.
If you installed your software 15 days ago, you can perform this with:

find / -mtime -16 -mtime +14 -ls