My brother-in-law just picked up a 1990 Saab 900 which runs well and
has fairly low mileage.  However, it has some issues with the brakes
that he asked me to look at since I'm considerably more car savvy than
him (I probably would have passed on this car, low price or not, if
he'd asked me.)

It seems that something about the power brake booster has failed.  The
brakes work, but he's going to develop some pretty strong leg muscles
getting the car to stop presently.  I'm familiar with late model VW's
and Chrysler vechicles (because I own them), and I have to say, I've
NEVER seen a brake cylinder set up that looks quite like the one in
this Saab.  (Even my 1995 Eagle Vision, which has ABS has a fairly
conventional looking master cylinder, which connects to the ABS system
separately contained.)  There were a number of sensors into various
points in the master cylinder.  What on earth are they for?  And is it
possible that the failure of one of them is causing the servo to not
build pressure for the power brakes the way it should?  I don't see any
real evidence that this car has ABS, but is it possible that these
relate to ABS in some way?  Did Saab's come with ABS in 1990?  Where
should we begin looking?