In '94 whenI had to replace my turbo, Turbonetics set me up with a To4B S3 Trim Compressor section, a watercooled center and clipped stock turbine.
I have noticed no difference in WHEN it starts to build boost, but it does build faster and harder, with more power on top.
When I go UMS and bigger injectors, I will get a To4E/T3 Stage 3 or 5 exhaust, since I will be putting in an external wastegate and 3" downpipe.
I don't want to choke off the upper end.