I'm pretty sure (but not positive) that it does but it only takes a little while for it to relearn. The ECM is constantly adjusting the how-I've-been-driving params, so you won't really lose anything.

Be aware the the ECM will also forget engine tuning params. The engine will run a little rough until it relearns. This doesn't take very long.

Details of what happens during the reset procedure should be in the FSM (link in my sig).

PS: The emissions system readiness will probably be reset also (see FSM to verify). This takes several drive cycles to show ready. Shouldn't be a problem unless you have a smog check done very soon after the reset.

PPS: The FSM is your friend. Download a copy and keep it handy.

?????
 

You could use a tune but a new ECM is not necessary.

I have the same aftermarket items as you (less headers) and while there is an improvement in all aspects of the car (acceleration, fuel economy, butt dyno, sound, etc), I know that there is a little bit left to squeeze out of these add-ons. In the few times that I tracked the car last year, it seems that the engine has a little bit more to give, especially at the top end.

This is one of the reasons that I am finally going to be getting my car tuned at Dynosty in a few weeks. Even though I love the way the car drives, I've been told that there will be a big difference in throttle response, and should eak some more HP/TQ out of the VQ.

If you are finished adding on to the car, I would recommend getting it tuned to get the most out of what you have. I'll know the results in a few weeks on the way to ZdayZ.

Keep us posted as to what you end up doing...