Quick answer: True or false if you have a socketed ECU and have the stock chip in it
 

The dealership will not be able to tell that the ECU has been modified without opening it.

True, AFAIK... how would they be able to tell? But I am not 100% sure I suppose.....

They log your MAP sensor and tell you to get lost.

So the real only "fool proof" option is having 2 ECU's and swaping them for service?

False.

And hope they don't read the forums.

Why? I'm not chipping my car and even if I were it's not under warranty. :)

If you have the stock chip in it, there is no way they can tell w/o opening it...
 

Think of the socket as an extension cord, there are no other electronics between it an the ECU (at least in the case of GIAC, and I'm assuming all others)

So then why you bothering asking?

1: My own curiosity 2: Information for a friend.
 

Thank you for your input.