Hola, Parra, no tengo experiencia práctica de meterle mano a una GS, y menos de ABSectomizarla. Como bien dices, la parte hidráulica es igualita, y en la parte eléctrica, por lo que he podido leer, en este caso no necesitas ni siquiera un relé extra, sino solo reconectar algunos cables del conector del ABS. En este post de una web de geseros ingleses lo explican bastante bien:
Simple, NO COST servo removal of 1150 IABS system
Te copio la parte fundamental:
1) Remove the blue ABS relay from the fusebox. This will extinguish the 'Brake Failure' warning light on the dash and as a bonus can be used to operate the brake light !! (no need for new switches as in other methods )
2) Strip back the sheathing from the ABS multi pin connector - identify wires and connect as follows
a) Grey/White wire (tail light feed) Grey/Black wire (12v feed) cut both and join together - thats your tail light sorted.
b) White/Yellow wire (front brake switch) and Yellow/Green wire (rear brake switch). Cut these two wires and join them to link brake switches
Now the wiring to the redundant 4 pin ABS relay
c) Pin 1 - Connect white/blue wire
d) Pin 2 - connect the THIN solid brown wire in the loom to provide a ground ( careful here - there are several brown wires c/w coloured traces and a Thick brown wire)
e) Pin 3 - Find the Yellow/Black wire and the solid green wire. Cut and connect these together and then to pin 3 of the relay
f) Pin 4 - Connect grey/yellow (tail light feed) to this pin
That all there is to it - you now have working brakes and lights.
Si hay algo que no veas claro, no dejes de preguntarlo, necesitarás algunos conectores faston para hacerlo en plan profesional, saludos