The more I see your responses, the more I'm beginning to think you don't know much about electrical systems. You're not seeing 4500w. Let me say that again, you're not seeing 4500w. If you're charging at 14.6v and dropping to 13 or 13.2, you should be concerned. A 370a alt should be able to sustain a fairly large load.
That's why I said clamp it when it's hot. A hot clamp will show you the true power your alt is producing. A cold clamp is false number. In fact, you should clamp the 4500 as well. I say this because if you clamp only 2500w out of the amp and your dropping to 13v, you have an issue. That's when you need to clamp the alt and see if it is indeed pushing 370a at peak demand, because it sounds like it isn't.
I'm trying to help and you're getting really, really offended. No joke, dropping that much with your setup is concerning.