STOP : WRONG - before you go playing around with those pedals, check something else first. If your pedel is steel ( vs alumimmmmnnn) use the magnet test. An Elephant could stand on that pedal before it bends, and I don't think you have had any Elephants driving your car latly.
Your problem sound very similar, to when just before my clutch release lever broke. My car became more difficult everday i drove it, until the lever broke. Based on experience you can not always tell if the, ' clutch release lever ' is broken until you loosen the nut and start to dis-assm then it falls apart and you know it is broken.
I would check this first, the check your cable, put the alignment pin in the shift assy, and the just your shift cables to see if they are aligned correctly, The proceedure is about the only thing the Haynes manual is good for. write me back at firstname.lastname@example.org let me know what you find,
Fieros are just street legal racing go karts