the mexico was just an escort with a 1600 cross flow with twin webers
most people fitted an a2 road rally cam to improve performance and some fitted twin 40's
induction kits have nothing on twin 40's sucking in air
the rs1600 had the bda engine
As said brake fluid is hygroscopic - moisture absorbing, so over time the brakes degrade
having the fluid changed will either sharpen the brakes or maintain them in good order
at least you can be confident there's no air or moisture in there