So I just heard from the shop (Barney Brothers here in GJ) that the radiator was clogged with all kinds of gunk, externally! They were able to flush it out and it seems to be cooling like normal again. I'll need to hook up the trailer and verify that we're good to go.
I did a lot of reading on forums and this is a common issue, guys have replaced water pumps & thermostats and no fix. I did see that Mishimoto radiator and the increased cooling, but did read a post where a guy has installed that radiator and not long after install, one of the seams split and dropped all the coolant!