Swap out the polini 43mm for a DR 43mm, and add on matches heads for both.
You're going to want to rebuild both bottom ends, as Aaron said. Pulling the motors to do the top end and not servicing the bearings and seals in these VERY simple motors is criminal. While in there, there is power to be gained from porting the intake patch, but if you're just trying to be mild, don't bother trying to drill the intake open for what ends up being less than a mm gain. The patch is really where the power is.
You're going to also need to tune your clutches and variator, and while you're at it probably want to swap to an aftermarket variator with tunable weights.
That exhaust you chose is going to be load, as are any circuit pipe. If you're going for quite, get the Gianelli stock+ pipe on treats, pulls great, very linear power.
There's a lot of reading to be done here, so use the search function, look at some past threads, and post a picture of your bikes. Even labelled as "Deluxes" they may have been swapped to single speed which will change certain things, as well as explain why they're only going 22mph right now.