[JLMounce]

I'm not saying that a mail order tune is bad, but is there a reason that you think a mail order tune would by default be better than what you've achieved yourself through the driving and tweaking process? Especially if the car is running better than it ever has.

As far as the mail order tune goes, you're going to be overwriting the tune you have in the system now, so even if the learn function is still active it will be attempting to achieve the commanded inputs for the new tune. It's not going to try and drift to the inputs you currently have in the system. If you get the tune and you like it a lot, I would recommend turning off the learn functions in the system. That locks out or limits your long term trim movement and you typically rely on your short term trims for adjustments due to weather and altitude changes. You do however have to them be mindful of making any changes to the car that could effect the tune. From engine part changes to even driveline changes like a rear-end gear change.

If this car was late model mustang, camaro, challenger etc where everyone is working with the same parts and the same engines, mail order tuning can be great because they are derived from tunes that the companies have developed on a dyno and through road testing. It's hard to go completely wrong as a result. For a traditional Pontiac that won't have a plethora of tunes out there, I'd be a little more hesitant. If you don't trust your own skills and tuning, I would actually suggest spending a little extra and having it tuned locally by a competent tuner on a dyno and on the road.