Booster Problems Will Not
made you to "pump the brakes" for any Low Pedal problems.
Booster w/o Vacuum
can, often will, made you "Stand on the pedal" often w/ both feet and even then barely stop the car. Try push the pedal w/ engine off... Booster w/ good check valve keeps enough vacuum to let you push easy ~ 1 to 3 times then gets very hard to push. But You having Low Pedal maybe only 1 time then goes hard to push.
IOW Something else is wrong...
If your not leaking fluid anywhere you see then:
Iffy rear pistons causing too much pad clearance.
Iffy MC w/ bad seals internally.
(Most likely, can be other issues too adding to low pedal.)
Worse... likely you have Pad(s) Dragging and "After a highway cruise..." the Brake Fluid can Boil as caliper(s) get hot. Very easy w/ old wet fluid.
See my Cave, Brake Fluid
Pad Dragging can warp rotor(s) or even cause a Fire and has done this to many people not just Fiero owners.
------------------Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)The Ogre's Fiero Cave
[This message has been edited by theogre (edited 10-18-2020).]