How many of you folks use some form of custom tune

[wagoneer]

As a newbee I am not sure if I am overstepping my position
Really curious as to how many members/nonmembers use one of the many custom non stock tuning mods available. I understand a vehicle purchased 12 or more years ago were factory tunes for the 12 years ago fuels and in some cases smog requirements of the day especially California. With the advances lower sulfer etc. Oil manufactored today are these
Causes to update a factory tuned PCM just curious