Originally Posted By: d00df00d
On an otherwise stock car, the reason there's power to be gained from modifying your tune is that the stock tune has a good amount of safety margin built in. Chipping your car dials out some of that margin. If you get a bad batch of fuel or some ignition parts start wearing out, you're that much more likely to end up with engine damage. And either way, you could end up with shorter emissions equipment life, more engine wear, etc.
Now, if you have other mods, you SHOULD get a tune, and it should be custom. That will help make sure everything runs right.
But on an otherwise stock car, I wouldn't bother -- unless there's something blatantly stupid about the stock tune (e.g. poor throttle mapping), in which case the tune should address ONLY that problem.
I drove identical drivetrains (Hemi LX cars, stock 2007 Magnum and tuned 2006 Charger) back to back, one tuned and one not...the difference was absolutely stunning. The car with the tuner had better throttle response, better transmission tuning, and actually used less fuel-despite a heavy pushbar and sticky 245/45ZR20 P-Zero tires (compared to GY Assurance 225/60R18's) due to more-aggressive cylinder shutoff programming. (It went from absolutely transparent to being noticeable if you were looking for it.) It had been tuned since ~5,000 miles without a problem...last I saw it, it was just over 260K. Only real change was that it now required (rather than recommended) mid-grade fuel.
