Fact or Myth...please confirm...

No_Brakes

So the other day I was showing my new 370 to a friend of mine and asked what he thought about doing a couple minor upgrades...intake, headers, and exhaust...nothing too extreme. I've always trusted his judgement when it came to cars, but this time I could use some more input. He recommended three possible routes based on my needs. One...keep the car stock b/c the power gains from those three upgrades would barely outweigh a perfectly tuned stock engine. Two...Install the upgrades and use the savings from doing my own work to have the car professionally tuned with newly appointed upgrades. And three...I quote, "get a twin turbo kit". Now the last one is a pipe dream and a half for me financially, but my question stands...Is the factory tuned engine a small decrease from an untuned newly upgraded engine? And if so, how much $$$ would a professional tune run me?

LMK!