SR20 research
 

So I was doing some research on the differences between SR20 turbos. From what I have read, there are 3 generations of the SR20 engine. The Red Top SR20 and the Black Top SR20, and then the Black Top S14. These turbos (as I read) produce safe boost till between 13-15 psi, after that they are past their efficiency range; this is on a Nissan 2.0 liter engine of course. The Red and Black top SR20 turbo's specs are as follows:
Compressor: T-25, 60 trim 56mm BCI-1 compressor.
Turbine: T-25, 62 trim 53.8mm 0.64 A/R turbine housing.
Center Section: Journal bearings

The Black Top S14 uses a slightly different configuration:
Compressor: T-28, 60 trim 60 mm BCI-1 compressor in T-04B housing
Turbine: T-25, 62 trim 53.8mm 0.64 A/R turbine housing.
Center Section: Ball Bearing

There is also an S15 Black Top that I didn't find much info on. My point is this: I have a SR20 T25 on my car now. From what I understand I should be able to leave my turbine housing bolted to my DP and Mani, and do a CHRA and Compressor swap. This would convert me from a journal bearing CHRA with a 56mm compressor, to a ball bearing CHRA with a 60mm compressor.

The 13-15 psi factor was an efficiency range on a 2.0 liter nissan engine, but what would it change to on a BP 1.8 liter? Lets say I am running 14psi on the SR20 turbo, and I do the conversion and run the same boost. What kind of power increase should I expect? Is anyone on here running the S14's ball bearing turbo on their miata?