94 Jimmy power issue

I have a 94 S15 Jimmy 2WD 4.3L W with the same EGR problems as everyone else, but that's not the problem this time. Everytime I idle with any lights, blinkers, or my AC/Heat on, or even pushing the brakes, it seems to suck all the power out of the truck. It drops down to 10v or lower, especially if I have my headlights AND blinker on while braking. It's even stalled a few times. I tested the altenator and the battery and both checked out. Does anyone know what the problem is? Please help, I don't know what to check next and I can't afford to take it to a shop. THANKS EVERYONE

 

Are you sure the problem is electrical, could be a vacuum leak, as in the EGR if you have/had a problem there. If the idle speed goes down, so does the alternator output. Pushing the brakes should be a clue, vacuum leak.

 

I'm not 100% sure of anything at this point. I did notice similar problems when I was fighting my EGR valve, but not this severe. I had it tuned up and all hoses replaced about 8 months ago, I shouldn't have any leaks. If that is the problem, how would I go about locating the leak?