Lets say I want to add headers, new exhaust and air intake.
Is the OEM computer chip / area affected by enhancements?
Will it try to adjust air and fuel mixtures?
Would it make my truck run worse than before?
Is that stuff all 'talk' or is ther any reality to it?

 

The stock ECU and PCM will accommodate for the exhaust and CAI. But depending what engine you have, if you go any bigger than 3" on the intake, you should into getting a tune for it.

The headers will probably need a tune also, again depending on how much of a drastic change they are.

Other people will chime in eventually, so you will have more answers...

 

You can add all of the performance mods you listed without a tune and the computer will deal with it.
But with a tune you will get more performance from your performance mods.

Phil