With the new turbo vs old, what are the A/R, intake housing size, exhaust housing size, and so on. It sounds like you just put a snail on there that is too big for the combo. It isn't pushing enough air. Either that or the exhaust turbine is too big for what your exhaust is putting out so it is spinning slow. Or a combination of both.
White 1990 LX
302ci, GT40 intake, cat less h-pipe, bbk shorties, no smog, aluminum drive shaft, t5 world class, crane 1.7rr, comp 270hr cam, 24lb injectors, 340lph fuel pump, 100amp alt, and gt40x heads <-- BLOWN UP. TIME TO GO BIGGER!