When people say "you must tune it right" or stuff like that...How do you tune efi?, or are people talking about going to a dyno and getting a chip burned??
They are usually talking about getting a chip burned for when you put on a poweradder of somekind to your ride. It is of greatest importance that you know your air/fuel ratio when installing a power adder. I think that it is better to be safe than sorry with a tune.
usually tuning refers to setting the a/f ratio across the rpm range. Also, in addition, other things such as spark timing. It can be easily done at most dyno shops or if you want to shell out some money for a Tweecer or similar
It is often also used for drivability reasons. After an HCI install, one's car might not idle worth a poo anymore - changing some parameters helps with that.
It can also be used to turn things on and off in the computer (emissions equipment, limiters, etc).
When I talk tuning I mean the actual tune on the car. Timing, TPS setting, and fuel pressure are critical. Then you get into other stuff like plugs and wires, making sure your cap and rotor are working properly, the right stat and operating temp.....there's a lot to it. I would estimate that 8/10 guys that get chips don't need them. I think that most, not all, NA guys that get chips don't need them.