Also, if you want to be happy, you should stop worrying about the kW rating.
Tesla is selling you values/results, and using components that live up to those numbers. If they don't have 77kW batteries the day your car was built you might get a 82kW battery because there's no way they're gonna stop production. If you focus on whether it lives up to what's promised instead of worrying about if your neighbor got some parts that are better then you're much more likely to be happy with the car.
Also also: There's speculation that the 82kW battery has a higher internal resistance, so while you might get some more potential range you might also be stuck with a car which is just plain worse at low SoC. So again, if you want to be happy, don't go digging before you actually find something wrong.
I can almost guarantee that Tesla won't give you a new battery as long as the one you have meet the expectations, so there's no way to go from disgruntled to happy.