Fluctuating RPM w/stalling at times?

[kandyflip445]

Well I finally got my S13 tags and now this is happening. I just installed subs in my car and I checked all the connections, everthing is fine there. I didn't drill through anything when I made a hole in the firewall for the power wire. I'm going to run an independant ground direct to the batt. when I get the wire for it. Right now it's grounded to the chassis With a hole I drilled into it. I sanded off the paint where is makes contact. I didn't hit anything drilling through there either. I made sure to check everywhere I did drill. My power wire runs on the passenger side under the carpet near the door (near the ECU?). I'm gonna be checking for vacuum leaks soon and make sure all my fluids are good, also. Any idea on the RPM thing is welcome.

The RPM fluctuations only happen when I slow down or am at a stop(not on the throttle). When it happens The lights tend to dim with the RPM's. It will be at 750 normaly and then drop to about 500, go up to 1000~1250 and repeat until I either get on the throttle or it just evens out. The lights dimming made me think that it was the connection to the battery but it isn't. If anymore info is needed then just ask. If you need numbers tell me what test I need to run. Thx.