Drawing too much current!!

Hey guys i have some problems that are starting to get really annoying....all electrical if you can believe it . First is what i feel to be excessive draw from the headlight/tail light circuit. I have a 130amp 3G alt conversion with all the proper power wiring to the solenoid...etc. Without my headlights on, the voltage gauge always stays right in the middle, if not slightly above. Once i flip the parking lights on (first click) i notice a huge drop in the voltage gauge...and it drops a little more when i put the headlights on...almost one full mark on the gauge. I believe its pulling enough current so that the battery isnt charging at low idle with the head lights/ tail lights on.

It didn't use to do this. Since i put the 3G on the volt gauge always stayed right in the middle even with the lights and heat on at low idle. Now i have this excessive draw? Where should i start tracking this down. Does anyone have a diagram that shows the routing of the head light / tail light circuits? I need to figure out this wiring crap...its really starting to annoy me! Thanks for any input!

Thanks for the info guys. I'll let you know what i have done so far....not much yet.

I have two different 3G alts that i have tried to see if it was indeed a alternator problem. Both alt were tested good. Both gave the same end result.

This is weird, i blew a rear right tailight bulb a couple weeks ago. So i puled the panel and replaced the bulb. The blown bulb had one contact that was nearly melted and looked to be the cause of the bulb failure. (filament was still good) So i replaced the bulb and check the wiring real quickly. Nothing apparent, but i didnt get that far into it at the time.

When i step on the brake pedal i get a notable drop in voltage again on the stock gauge. But this makes me think there might be an issue with the tail light circuit. too much resistance in the circuit or something? all the interior panels were out of the car a few months ago to weld in the roll bar/cage and might have pinched or frayed something going back in. this is why i asked if anyone had a diagram or location of the tail light circuit.

I will test VBat with a DMM and see what i come up with anyways! Thanks for the advice! Keep it coming!