Yes, the original stock alt. and the new one do the same thing. I'm also stumped and don't want to throw another pile of money at a new alt. and still get the same results because I missed something. Having the Duratech kinda sucks because of access to the alternator, it's not like I just pop the hood and unbolt it.So it hasn't been tested outside of the car. So I would yank it out and have it tested. Wonder if its something weird with your electrical system.
I'm a bit stumped here if both the old and new did the same thing.