Stock Alternator, what's it rated at?

[Razr]

Well there's no specs that I can see on the alternator itself, but based on it's (small) size alone I wouldn't expect it to be rated at much more then 60-70A short-term, but who knows what it'll do at higher duty cycles..

The big question is how much reserve does it have? Especially considering the fact that Yarii have electric power steer, so more static load than most cars.

If your Yaris has a rear window defroster and electric windows it's a gimme that you'll have 20-30A you can borrow from those though.