When I have the car at idle sometimes the rpms jump a little 1k to .5 back and forth and sometimes it dies out of no where. But this time it died and wouldn't start. I turned the key nothing. Waited a few minutes starter clicking and radio came on. Then I got a jump and it fired right up. Could this be a bad starter battery or what I think is the ultra lightweight pully I had installed? I checked terminals they were good ground good so I'm lost and I don't want this to happen again. I have a 02 Wrx Cobb stage 2 ots maps. To check engine lights on. But battery light was on while this was happening.