[Acesanugal]

Well, what year is your car? N/A or Turbo?

- S4 systems are "velocity" (speed) sensing tech.

- S5 systems are the cheapened engine speed (RPM) setups that Mazda went to for all S5 N/As.

- S5 TII's retained the S4 velocity sensing systems.

So...

The 86-88 systems are velocity sensing, known as " 3-line ", while the 89-91 engine-speed sensing are referred to as the " 2-line " . This is literal. Bearing in mind that both racks and pumps have a non-pressure return line at the reservoirs, it counts as one line. S5 power steering systems are 2-line, because there will only be one PRESSURE line and one non-pressure RETURN line. As you can probably imagine, 3-line systems have two PRESSURE lines from the pump to the rack, and one RETURN line -- naturally.

As for which of your lines is the pressure line(s) -- assuming left-hand drive -- the pressure lines on an 3-line rack are closest to the inner tie rod.