I'm moving up to a turbo on my 7 that is designed for 20-25 psi, so mine is up for sale. When I used this turbo with a 3" downpipe into a 2.5" Y-pipe I've seen 19 psi at 3500 in fourth with this setup. VERY responsive!
The turbo has:
.70 compressor side
.84 hot side fully divided
P trim wheel (New wheel installed roughly 4000 miles ago after I bought it from another RX-7 owner.)
It is oil AND water cooled.
I drilled/tapped holes in the compressor housing that I used as pressure sources for my water injection kit.