When searching for a way to increase the frame rate of the game in Google, in BGEE (not BGIIEE), we can find an old Mac OS X support thread
that is now archived and that only terminates in "cheat in speed boots".
I wanted to open this thread to give a partial solution.
I'm using Baldur's Gate Enhanced Edition on Linux. I don't recall the exact version but I've purchased it only last week (around 2016/04/01), during the sale undergone for the new expansion Siege of Dragonspear.
I have had a problem when first adding the line
'Program Options', 'Maximum Frame Rate', '45',
(The default value is 30)
To Baldur.ini (file that should be in your personal configuration folder, it is under $HOME/.local/share/Baldur's Gate - Enhanced Edition/ on Linux).
This file is overwritten when launching the game, rendering void your effort.
However, there is another file, Baldur.lua that can be found in the same folder. If not, you can probably create it and append inside the line:
SetPrivateProfileString('Program Options','Maximum Frame Rate','45')
It is working as intended, during a quick test.