A tune is needed for many reasons.... Biggest being making timing and fueling safe for the power levels your at.... 12.1 fuel ratio might be fine at stock but definately is not ok at 400hp.... and other things like stock torque management and traction control make your car go crazy lean when they activate.... this is fine at stock power levels but is definately not ok at 300+ hp.... not to mention stuff like how the stock tune leans out the fuel mix the longer your at wot.... again this is kinda sorta ok stock but when your making big numbers its bad to go lean in the middle of a pull.... and then theres stuff like speed limiters and transmission settings. Trans settings alone can completely change the feel of a car.... If you ask me its almost always worth getting a tune once you start dropping pullys and beating on it.
