Isn't your appointment to get it tuned coming up soon? Hopefully that will take care of some issues.
What I have seen lots of people do is to get some add-ons put on a vette, get it tuned for those add-ons, and then when it comes time to sell the car, they take off the after market stuff so they can sell it as being "bone stock". But they don't normally reload the old tune back in. So the car will run OK, but the air/fuel tables are a bit out of whack.
Disconnect the battery, then hook it back up again, start up the car and see how it runs. If it sputters and runs rough for a while, it has a tune in it that isn't optimum for your engine right now. The fuel trim tables will get filled with new data to self adjust the A/F mixture and it will run better in a few moments. I saw that phenomenon on my C5Z after certain "tuners" fiddled with it.
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