^ That was just a preliminary check before I tore everything down. I confirmed with the crank gear later. I also set tension and everything with the crank gear, before installing the pulley.
Can you elaborate on your last two sentences? The water pump and pulleys are both brand new out of the box. This is my first TB/WP job, but I followed the tutorial to the T. I didn't see anything else I needed to do when installing these.
To sum up where it sits now...look at the photos in the links I posted. Looks like my problem. For whatever reason one of the idler or tension pulleys has to be canted causing the belt to ride the back of the gears. It has to be one of those pulleys...they're the only pulleys in the system that were changed, and the only ones that could be canted. Most likely defective water pump, or some debris or burr under a pulley. I've seen so far 5 or 6 cases on Miata.net where a WP was machined out of spec and a new one solved the problem.
I'm going to just bust everything completely down tonight providing it's not raining...stupid small garage. I'll do everything in my power not to disturb the crank bolt/locktite patch job. Thing i'm curious about is how I tell if the surface of the WP is machined 1/4 of a mm off... Buy a new pump and use trial & error I guess, and hope the new new pump isn't off as well. It's going to be a fun weekend, hope I get lucky.