[Edit: I am not sure how this ended up in DIY Guides, mods please move. Or I guess I can take some pictures and make a DIY out of it to add to the existing great guidance on here already

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I have used Gates in the past and from the description it was unclear as to whether it had a metal or composite impeller. It came yesterday and it is metal. It comes with a non-metal gasket as well, that was broken, and there were tool marks and dings on the mounting face of pump. When I rotated it, there was quite a bit of resistance (I understand this is normal) but I could also feel a slight clicking or kind of a movement, it is hard to describe. So it is going back today. It was an interesting experiment.. and I guess the result was as expected. (We used a gates when we did the timing belt/WP change on my son's Miata and the experience was different, it was all good, maybe they use different vendors/manufacturers to make the actual pieces)?
So I ordered a Pierburg water pump from p a r t s g e e k . c o m for $225.23 with free shipping, that is the best deal I found on that pump by a decent amount.
I had already ordered the WP Gasket and Wahler low temp thermostat and gasket from Pelican and that came in yesterday as well.
I was going to do WP/UD Pulley/ Low Temp thermostat over Thanksgiving but now it is moved to Christmas break
Moral of the story - I knew better but wanted to find out for myself anyway