Before you disconnect the battery though, take it to an Autozone and have the code checked out. They do it for free. If you suspect the fuel filter, then change it and see if that makes a difference. Personally, I try to change mine every year. Since you still have the occasional surging, I'll bet you've probably got some lean left/right bank codes. Sounds like a vacuum leak somewhere. Check for any hardened/cracked vacuum lines. Good luck.

Alin