Hi,
I don't know what you mean by "changes required for using postgresql" unless perhaps you have not seen the updated documentation.
http://www.mojoportal.com/settingadatalayerreferenceinvisualstudio.aspx
In the old days one had to make changes to project references but not anymore, you just choose the correct build profile.
For pgsql you choose either Debug - pgsl or Release -pgsql from the profile list.
If you manually changed project references then you broke it.
Hope it helps,
Joe