So since Zach suggested it, let's post up what we know.
Power steering pump: The 4WS pump is larger than the 2WS counterpart.
Front swaybar: The 4WS front swaybar is 20mm, whereas the 2WS is ___mm?
Rear swaybar: Rear swaybar has different mounting style (As it has different endlinks). Is ___mm in size, while the 2WS version are ___mm in size.
Rear endlinks: 4WS have a hybrid endlink system, with the standard nut/washer style on top, and a "tie-rod" style on the bottom.
Fuel tank: The 4WS models come with a tank that is split down the center, allowing the rear steering shaft to come under the center of it.
Fuel pump: 4WS models have a 2nd fuel pump, known as a transfer pump to pump fuel into the one side when the other bank runs low.
Cosmetics: 4WS models have "4WS" labeled on steering wheel, and noticable 4WS stocker on rear trunk lid.
Power steering rack: 4WS models have a different front PS rack, and have the added bonus of a power steering rack in the back.
Electronics: 4WS models have additional electrical boxes under the seats, such as the timer module under the passenger's side seat.
Suspension: 4WS models were not offered with AAS suspension as the 2WD versions were, but were given a RSTB from the factory. They also did not come with a lower tie bar, as none of the 89's did.
Year: Only offered in 1989 as the MX6GT, while in 1988 the 626 was offered in a 4WS version (Only blue interior/white exterior)
Production numbers: If anyone could get me these, Id be amazed.
If anyone can fill int he blanks, correct info, or add more for it
Ive been sick and out of work for a few days, so Im just being bored