(Addendum to previous post)

I'm familiar with the engines:  The 2.0Si had a B20A5, 135HP 1958cc,
whereas the "Si" had a B21A1, 140HP 2056cc.  The 1990-91 "Si" had two
different "Special Edition" models:  ALB and 4WS.  Mine is the ALB.  I
can pop the hood and see the anti-lock brake module sitting behind the
battery to the left of the distributor cap.  Of course, I've also put it
to the test once.  The ALB kept me from having a nasty accident...  I
originally had the B21A1 in my car; but as I mentioned, I replaced it
with a JDM B20A due to extreme oil comsumption.

You are correct that there were far more 2.0Si's manufactured. The
1990-91 ALB and 4WS models are hard to find...  I felt lucky when I
found this one...that is until I realized how much oil the B21A1 drank.

I owned a 90 Prelude SI,and there was a 2.0SI and a "SI";the difference was
that the "SI" had 140 HP(that's the one I had),and the 2.0SI had
135HP,though both were 2 liter motors.
I suspect most of those "Prelude SI" are the 2.0SI models,they were much
more common. ISTR that the 140HP motor was an all-aluminum motor,no iron
cylinder liners.

I don't recall the 90 SI as having anti-lock brakes,though.

I have a 1990 Prelude Si ALB with a JDM B20A engine in it.  (Engine is
not the original, of course)  My ECU is a PK3, which is the original ECU
from the factory, and the car runs fine.  I've noticed that most 89-91
Prelude Si's have a PK2.  Does anyone know the difference between the
two types?

Thanks!

Jon