did you ever get that injector replaced?
did it solve your problems?

while you are working on stuff, you should make it so your injectors don't have power all of the time. Here's a good write up I found
TwinTurbo.NET: Nissan 300ZX forum - The simplest mod so far... switched power injector rewire.
a lot better than doing that wire jump thing that most write ups tell you to do.