CT-12,
it flows batter then ct-9 but its not the worth upgrade, its weaker then ct9,
Ceramic exhaust blades shatters very easily, if you hit frequent rev limiter , ull break it, they are good till 1.1 bar of boost, reliable till .8 bar.
I will not recommend installing them,
The Best turbo I know are
TDO5H spools at 3300RPM (TDO4H too)
(1.3 bar, 5efhe, 440cc, low comp. Safc, 4efte electronics, fmic, fcd )
on this same setup we had Nissan S15 turbo as well, T-28, single BB, was good but died early,
KKK K26 spools near to 4000RPM
(5efhe, 440cc injector, 4efte electronic, safc, fcd, 1.1 bar)
GT28, spools at 4000 RPM
(4efte, 1 bar, Safc, fmic , fcd, 440cc)
TD05h is very reliable turbo. KKK stand next to it. Both of these turbo kick in very hard.
How much Boost you want to Run?