ousteroune, first check baldur.i.ini to see if the "Low Mem Sounds" fix is still there. For example, if you run BGConfig to change something else, some of the settings in baldur.ini may revert to default values.
If the fix is still there, try installing Generalized Biffing, unless you did already. On some hardware it can really make a huge difference in performance if you have a lot of mods installed. Unfortunately, currently the Spellhold Studios website is down, so you'll have to wait for it to be back.
Incompatible mods can cause all kind of problems (bugs, crashes, etc.), but don't usually cause slowdowns, unless you have too many files in override, and this is usually fixed by installing Generalized Biffing.
Edit: fixed typo.
Post edited May 04, 2014 by Ergos