420A Check Engine light

[Flamennn]

I have a problem with my engine the check engine light is on all the time. ive done some research and its blinking codes:
12: airflow sensor.
31: Knock Sensor it says that's on turbo models but mine is non-turbo 420a.
43: EGR?
55: Idle air control valve.
i took it to auto zone and they checked it with a scan tool and it said random misfire. And that is true it does that randomly when i am driving.

Is there anyway i can fix these without buying new parts?
I also cant find out where these parts are at on the car.

I have another computer for my car should i try putting that in?
I also have a spare coil pack with wires.

Can you help me? Please

 

[99RedGs]

Read this : Engine Misfire Diagnosis

 

[luv2rallye]

Your reading the wrong codes for 2gNT. See here: 2GNT.com - PCM_Error_Codes

 

[bryanwheat]

Check all vacuum hoses and change coil pack

Probably a good idea to do some testing before replacing parts don't you think? I would spec out the coil and wires and throw some new ngk copper plugs in it.