2001 Pontiac Grand Am cylinder misfire

Hello I have a 2001 Pontiac Grand Am, it is the V6, 3.4 fuel injection model. A few months ago I began getting the service engine soon light come on.
I replaced my spark plugs and spark plug wires as well, the light went off, but eventually came back on.

I eventually found a auto store that would check the codes for me, they discovered that it was a cylinder misfire, so they recommended some high quality fuel injector cleaner, and the light went off, only to come back on later.

When i went back it was a different cylinder misfiring, and I also went to another dealership and there it was a third different cylinder misfiring. Anyway the light went off for a while, but it would come on occassionally here and there.

But recently I have been getting horrible gas mileage and just today I was driving and my engine was jumpy, and stuttering, and then the service engine light was flashing and the engine was stuttering even more. I took the car home, checked online and it said to check plugs, wires, other related Sh!t. The plug wires are fine because touching them with the car online sparked them, so thats as far as I am with it, If anyone has any suggestions please try and help me, this is the only car I have and with school starting in 9 days I am worried that I wont have a car...

thanks, Justin
The plug wires are fine because touching them with the car online sparked them what i mean is that we started the car up, pulled the wire off of the plug and touched it to metal to spark it, someone suggested doing this to ensure that the plugs were working fine...
What brand plugs did you use? And did you buy the cheapest set of wires you could find? It is cheaper in the long run to invest in good quality wires up front. OEM (A/C Delco) plugs are the best bet also.

Being way2old is why I need help from younger minds