car dies.....help

[fuzzydice]

i just put in my pbm coilovers into my s13 and suddenly my car/battery will die while driving. my brother had this problem on his s13 and we never found the cure... i rubbed into 2 wires in my front left fender due to me putting it to low but i fixed those and it hasnt changed.... i tested the load (12.9v while the car is off) (12.3v while running) i dont think it is the alternator because when this happend to my brother i swapped him alternators and it worked fine on my car but his car still had the same problem.... any advice as to where i should start would be great