My turbocharger candidate list is still open while I try and find an upgrade that fits what I am looking for. A potential contender is a revised FrankenTurbo F21 that Frankenturbo released some early prototype photos of.
A revised, billet, compressor wheel:
and even more interesting, a mixed flow turbine:
This looks to be an excellent combination for trying to maximize power on a stock motor while retaining good spool up characteristics.
Time will tell if the prototype lives up to the design goals.