1986 Pontiac Fiero tachometer is registering incorrectly

SOURCE: fuse blowing

I agree. I would start by inspecting from the tail lights wiring and move up. You will have to remove interior pannels to see the harness.

SOURCE: tail lights fora 1986 Fiero

rear of the car is totally different, if you want to do the gt conversion you will need to exchange the whole rear clip.
gt light are wider,cant use just the lens or cover.check for parts at vegas fiero club

SOURCE: Speedometer stuck at 20mph on

I have a 1985 fiero and had the same problem. Fiero do not have a speedometer cable the speed is sent from a governer on the tranz to the gauage. So in short the gauage needs to be replaced.

SOURCE: need a wiring diagram for distributor for a 1988 pontiac fiero gt with a 2.8 v6

There are two plugs which are plugged into the distributor one is a two wire  and one is a four wire. the two wire has a pink wire on terminal A and a white wire on terminal B these two wires go to the remote coil  black plug The four wire has a black wire with a red trace on terminal A A tan with black trace on terminal B A purple with white trace on terminal C A white wire on terminal D

SOURCE: tachometer on my 1986 fiero gt is out of

There's a good chance that the tachometer switch setting on the tachometer is broken. They use the same tach for different engine sizes and change the amount of cylinders with the switch. You might have to replace the tach