After comparing a few part numbers the only change I found was the ECM. Reeds and injectors were the same part number. A new part # usually indicates a change. The ceramic coated muffler is being marketed as new for 2019 could be different than previous years. A/C has a past of making a lot of little changes and not telling anyone, they are getting better at marketing the changes but still need to improve. The 19 will be better than the 18 and the 20 will be better than the 19 and so on. Continuous improvement is what it's called.
I stole it from the EPA!
Found it on Dootalk....
It is a spreadsheet from the manufacturer's submission.
Doo reports in NM and all other manufacturers report in KW