I do find it odd that a shop would do an install and not have a tuner lined up for you. I sell a lot of Mail order tunes but its only with HP Tuners. The more you do to the car, the harder it is to make the mail order tune work properly. With bolt ons, its easy to do. With forced induction, I really dont do mail orders on because guys mix an match parts so much so much can go wrong.
I know a shop that only does one kind of forced induction build and they use the same tune over and over again and just plus or minus some timing and fueling. That's crazy.
I would not "mess with the injectors" unless you have changed injectors. Then if you have, I use a spread sheet on specific injectors. You can just wing it.
If you use an cheaper off brand injector and they didn't supply the calibration data, it doesn't work. Ive seen local shops drill out injectors to flow higher numbers. That's great that you have 30 pound injectors that flow 40 pounds now, but where's the data I need for all the voltage changes and pulse strategies.
Injectors are where the tuning starts. If that information is not correct, the rest of the calibration will be calculated incorrectly.
If you have HP Tuners, I may be able to help you depending on your build. If you dont, google a dyno shop near you and have the car done right.
I hope that helps,