I am posting this up here to help answer the many questions a day I get about canned tunes and custom tunes. I am borrowing a good analogy that I read from Corey over PHP...
"A few times a week, a certain question passes across my desk -- sometimes in e-mails, sometimes by way of a phone call. I guess it's time to answer it on here with the hope that inquisitive minds will check the FAQs.
What is the difference between a stock/factory calibration, a canned calibration, and a custom calibration?
First, let me say that calibrations are also sometimes referred to as files or tunes. The terms are interchangeable.
Second, I cannot take credit for this analogy, but I've seen several people use it, so I don't believe I'm stepping on any one person's toes.
Factory tunes = buying a suit off a rack
Canned tunes = giving the tailor your measurements and having a suit made for you
Custom tunes = going to the tailor's shop so that you can be measured and fitted and choosing the fabric for your brand new suit
Or you could always look at it as:
Factory tunes = good
Canned tunes = better
Custom tunes = best
I am not saying that factory tunes and canned tunes aren't any good! However, those calibrations need to be written to cover a variety of applications. The same Ford truck might be sold to a guy living at sea level in FL who uses it for his hour-long daily commute or to guy living in Colorado at 6,000 ft. who primarily uses his truck to tote his camper through the mountains and into Utah! These two customesr obviously have different needs, and that's one way reason why someone might prefer custom tunes.
Finally, some people request custom tunes simply to make the most of the modifications they have on their trucks.
It's all a matter of figuring out what your personal needs are and the best way to meet them. "
^^Thanx Corey
Kinda simple, but it gets the point across very well I think.
So for all you that are looking in to a plug and play tuner/flash device please read this and think about your decision before you make your purchase to ensure your hard earned money is going to the place that will benefit you the most.

Do it right the 1st time.