No need to get a pipe your stock pipe will work great if it wasn’t modified to begin with
Pitch the stock air filter thing with the restrictive resonator to get a metal mesh filter, Dremel out your intake to 14 mm or post for one on Buy+sell, up jet carb to a size maybe 62-63#, W 212a atomizer or best bet get a 14 mm Carb and around 68-70 jet 212a atomizer
Drill around 1/4-5/16/ hole down into the exhaust and one into the cap I use a drill bit extender In picture
Sand or mill head flat
And you get this
Of course you have to remove the pin in the speedometer which is not an easy thing to do so it will read past 30
Before you do anything make sure your magneto is serviced and your timed correctly so read this completely
https://www.mopedarmy.com/wiki/Puch_timing
I like around 18° with this set up
I got two bikes with the set up one with a 12 mm carburetor and one with a 14 mm carburetor and they keep up with kitted bikes (not ones I kit though)