why does my 1985 pontiac fiero gt die?

[dsflettersornumbers]

i have a 1985 pontiac fiero gt that ive been having problems with. i got it out of the shop and had to have the guy self tap a screw to hold the (what i think is the distributor, what ever is under the distributor cap, like what the d-cap screws into) cause it was stripped, now i get it home and see that the distributor cap has a missing screw on one of the sides so i put a hex self tapping screw on it so it will hold the distributor cap down on the distributor, when i did that the car started bogging out and dying on me alot. and at about 4k - 5k rpms it like back fires and like gargles, now i changed the spark plugs, had my friends re time it, cleaned out the injectors with 100 octane gas/ used sea foam/ and some Lucas, but im still getting the same problems of it dying and like back firring at high rpms. now when i push the d-cap towards the Passenger seat itll start up fine and idle fine but if i let it go it dies so i dont know what to do my friend thinks its the fuel pump

 

[melsg5]

It sounds like you already figured out what is wrong, something in the distributor!

 

[Oreif]

Either the distributor cap is not aligned/sitting correctly (it shouldn't move at all when it mounted properly) or loose. Are you sure it's the correct cap for the distributor? At high RPM the rotor spinning inside can vibrate the cap if it's not properly mounted. If the rotor isn't the correct one or not mounted correctly that can also cause problems.
It sounds like something (cap or rotor) is messed up which causes the ignition to arc incorrectly. Is the distributor cap and or rotor new?

If the distributor has stripped screws and such, You can always change it out. Many auto parts stores sell reman distributors.

It's not the fuel pump. Back-firing is ignition related not fuel related.