i have a 95 in my 90. I didn't install it. it was there when i bought it.
here's what i've been told happened to mine.....
when putting a 95 motor in a 90, they must put in the 30# injectors so the engine would run transparently to the stock EEC. They also had to change the harmonic balancer sensor ring and some of the other sensors to the early styles.
good luck.
Jeff