mazdatrix sells to fuel pumps for the 86-88 and 89-91, s4 and s5 respectively. but why cant i use my 88 fuel pump in my 90 vert, it looks about the same, and if it will work with a little ingenuity, let me know before i buy a new pump please, thanks yall!

 

i think all 2nd gen fuel pumps are swapable and i know you can put FD pumps in FCs

 

I think the wiring is different. The S4 has 12v at all times while the S5 has alternating voltage. Now whether it will work or not, I don't know.

 

I believe the pump itself is the same. Just two wires...

For the record, almost all in-tank EFI pumps of the era are similar.