Do you even do any research before you start spouting off?
* Plenum has changed if you'd take five minutes to look at them side by side, you'd see they are different...
Attached photo of them side by side
* Air filter, while it is likely the same in size and shape - thus meaning previous year filters will filt, they likely changed the filtration material on the new OEM filter. Kawasaki has even stated that the filter will be new. Change in filter design = change in part number.
"With a new air filter, spark plugs, and intake chamber, power is claimed to be increased. We’ll be sure to have a true figure once we get to roll this model onto the Cycle World dyno. In addition, Kawasaki is claiming there is no mpg penalty for the increase in power."
Spark plugs have changed... again, if you did some research you'd see on the 2018 model they were NGK SIMLAR9B9s while on the 2019 model they are SILMAR9E9s.
SILMAR9B9 info: https://www.ngk.com/product.aspx?zpid=41486
Cannot find info on SILMAR9E9s
Speedo is vastly different between the 2018 and 2019... So if you're saying they're the same, then it's obvious you haven't done a lick of research.
Attached another photo for you
The head has changed as well, despite the internals staying the same. From top to bottom the internals are the same. But the head itself, has a different part number too. I'm hoping that they maybe used the H2 SX head which looks to be a little bit larger:
Wishful thinking but hey, why not huh?
Exhaust the same? See the photo I attached previously as well as the side by side photos posted by others. If you'd look you'd plainly see that the header design has changed; instead of 1-2 and 3-4 being combined and also having crossover tubes between all four pipes, those crossovers have been eliminated and the cylinders are now paired differently with what looks to be a better designed collector element for more flow.
This is just the tip of the proverbial iceberg - a lot of things have been remove