So this was a non turbo engine that you added a turbo to! Do let the purists hear that. I think it was still mechanical injection in 95, not computer controlled, Right? What did you do for fuel enrichment? How different are the engine internals from the factory turbo models? are you monitoring the egt? how hot does it get? pre turbo or post?

Now the HX35 is a bit on the big side, but there is a way you could get it to spool faster, much faster, since the turbine housing is split. you would need to make a valve, that flips at a certain pressure. If you feed the exhaust pressure / gasses from the second bank of cylinders along with the first bank into the turbine inlet for the first bank, there will be a night and day difference. then at a certain boost level, maybe 7psi , the valve will then send the exhaust gasses / pressure from the second bank of cylinders to the back side of the turbine. kind of a wastegate before the turbine.

This is for a log manifold (Same concept) :


It feeds all the pressure into the front half of the turbine to make it spool faster