He cuz,
The chinese T28 turbos have not yielded great results for guys sofar, reliability, If u want mid range paower that goes through the range, go T28, if you want pig top end power, the T3/T4 is beter... All depends what u want.... The exhaust housing will also affect how quick it spools, too small and u will cause back pressure though.....
What are you looking for in a turbo? Robot to robot, quarter mile, drift, etc.... Check out the Garrett website for the Turbo 101, 102 + 103 write ups..... Very informational, then make a choice....
But make sure the turbo has 2 cooling methods, water and oil, well oil will be both cooling and lubrication, but try get one that is water cooled as well....
Turbo Direct seem to be pritty good, go see them to help build you one for your purpose, they can do a T28 bush bearing with simmilar specs to the GT2871 which should be more than sufficient.....
Also with manifold, the Turbo Toys style one will mean u need to move ABS pump, try get a custom one done like Aep sais, then they can make fit withought moving the ABS pump....
Hope this helps.....