I am having a problem with my headlights dimming while I am driving. They only dim when the car is accelerating and the lights go back to normal when I let off of the gas. I replaced the battery a few weeks ago and thought that this would cure the problem. It did not. I suspect it may be the alternator, but my interior lights are not dimming at all while I am driving. Fan belt? Any ideas or similiar experiences. Thanks.

P.S. I have an 04 LX w/ V-6 in it.