The Fiero uses an older-style mechanical flasher, so it is naturally a bit slower than more modern cars that have electronic flashers. Grounding issues is what typically affect how the flasher operates. I usually stick with the old mechanical style for my Fieros, & I clean all the grounds for all the external signal lights and also clean the contacts for the flasher itself. That usually gets it to 'spec', which again is still going to be "slow" because of what it is.
If you're wanting a more modern flash, or even a "ricer" fast flash, then you're going to have to upgrade the flasher to the electronic style. An electronic flasher can also allow you to run more modern marker lights, like LED, without further modifications to the flash setup. It's just simply replacing the mechanical flasher unit under the passenger side dash with the electronic style found pretty much everywhere.
First make sure all your turn signal bulbs are working because a flasher's speed is related to the amount of current being drawn through it. If one or more bulbs are burnt out (including the ones on the dash) there will be less current flowing through it and it will flash slower. Just be aware that the rear side marker lights in the rub strip aren't supposed to flash, but the rest are.