Nope, i'm afraid I don't get you either
In fact, as I type I think I kinda do get what you're getting at.
Correct me if i'm wrong.....
If both the turbo and NA operate at a particular level at sea level, and BOTH are subjected to the same thinner air at altitude, then why does the NA suffer more??
Lets say that both operate at 100% at sea level, and at altitude the air is 50% thinner (for example). Therefore the turbo will only operate at 50% of it's original capacity and so will a NA.
The fact that the turbo forces air in should make no difference, as it is only forcing in less dense air.
That what you are saying staz???
I think it will make a difference though. The NA is only receiving air naturally, so kinda only gets what's on offer. The turbo is having it forced in, and at sea level could probably force in more than it needs. So at altitude with the thinner air it manages to force in that bit more that it can't at sea level, therefore allowing for performance closer to that of sea level.
I could be totally wrong though!!