WTF???, Turn head lights on, Car runs like crap! Options

[aircooledboy]

This my friends is why I am STRONGLY considering an alternative powerplant. (IMG:style_emoticons/default/confused24.gif)

Here is my deal: Drove the teener to the salt mine last thursday. (1.7 stock d-jet) Car's been running VERY well the last 3-4 weeks. Unexpectedly rains like hell at lunchtime. Have a meeting across town so I gotta drive. In the rain on the way, car begins to really hesitate and stumble, doesn't want to go over 4000 RPM, even small back fires 2-3x. After lunch, rain has stopped, no more backfiring, but bucks a little at lower RPM (ie 2000ish), still real tough to climb over 4500 on acceleration. Get it home, park it, figure it will be ok when dries out.

Didn't drive again until this morning (mon). Upon start, same deal w/ RPMs, but as the car warms up, less and less of an issue, by the time I get to office, seems to running good as usual. Coming home tonight: Starts fine, runs fine, but as i am leaving the parking deck, I turn on headlights, STARTS RUNNING LIKE SHIT again. I stop in the deck, pop the lid, and I see the headlights shining on the wall are damn near going out as the idle dives (battery 12 months old). Rev it up, lights come up. Turn headlights off, idle smooths out. It's still plenty light out, so I start the drive home. Every now and then, while driving home, I pop the lights up, engine suffers. Get out of the city, going about 70, pop lights up, can definitely feel engine running less smooth, but no loss of power. Pull into garage, turn headlights on, still affects the smoothness of the idle, but just a little. Then though, I notice that when I hit the brake lights, the headlights dim slightly?

help me, help me (IMG:style_emoticons/default/sad.gif)

Grounds?, alternator?, buy a V8?? Electrical issues are hands down my weak suit. Suggestions about where to start would be most appreciated.

Thanks,

Chris