130 amps should be more than enough juice. You may have a grounding/electrical problem too. I have an ATX, that puts additional drag on the system at idle that your SVT doesn't have to deal with.
Hunt it down & you should be quite happy with the result when you finally find it.
By the way, I just replaced my alternator. It was in the process of going bad. Battery light would come on when the rpms were over 5500 or so. When cold, the headlights, interior, radio lighting would kinda dim & blink like I had a friggin' disco Contique thing goin' on.
(where's a barf emoticon when you need one)
