Ford Repair: 1990 cougar, firing order, gas tank

Question
I tuned up this car...rotor,cap,wires,plugs and air filter. I also added some
injector cleaner to the gas tank.  Now the car runs real rough. When I replaced
the cap & wires I did them one at a time. The car ran fine before that. What
could have gone wrong. I am unfamiliar with the vehicle.

Answer
You have the firing order out of whack. You must have done it when replacing the cap, it is easy to do. Even the best mechanics do it, but they have resources allowing them to fix it rather quickly. Here are instructions on your firing order.1~4~2~5~3~6 ~~~~~~~ front | 1 2 3 | of | | vehicle | 4 5 6 | ~~~~~~~ Distributor rotates counter clockwise