Why do you have to flash your computer for some cold air intakes and some say you don't ? Can anyone explain the differance?

 

I've never heard of that need before. IMO I would'nt worry about it if check engine light does not come on after procedure. In theory however I would think that it could have something to do with drastic fuel air ratio changes.

 

according to what i've read / heard it makes the car run too lean if you don't tune it. Because the computer does not know to add more fuel to the new amount of air that you get. But some parts advertise no tuner needed. if that is the case how does it add performance.