MOPED ARMY

You just leaned out your fuel mix. Puch air boxes are pretty restricted, and removing it allows more air to be blended with the gas. A lean mix will often result in increased rpm and power, however it may also result in catastrophic engine failure. The fuel is mixed with the engine’s lubricant (2T oil), and a lean condition delivers less lubricant to the cylinder and piston walls, resulting in increased friction and heat until the engine seizes.

That being said, 23mph sounds a little slow, depending on your hp rating. If you have the 2hp version, you should be able to go 30mph. If you can’t, with the air box on, you should thoroughly disassemble and clean the carburetor. Verify float height is correct and Check what jet size is in it while you have it apart. If yours is the 1.5 hp version, it’s top speed would be 25mph. 23 isn’t far off. Removing the air box would give you a lean condition as I described, and could be dangerous for your engine. There are instructions in the wiki for converting from 1.5 to 2 hp, if that’s the case

If you’re going to keep the junk restrictive square air box you also need to keep the snorkel that goes in the hole in the frame, and with a 2 speed usually its the smaller size one and you must use exact correct jet per hp,

(All that bull crap just to go way slower is so stupid I’ll never understand why people still use those stupid pieces of plastic)

I hate the square airbox/all Puch stock airboxes and most other brands too.

I put them in the recyclable bin by the 5 gallon bucket fulls for those are the restrictor/governor of most mopeds,

I use an aftermarket Mesh filter and most times an exhaust that has a chamber in it too, I jet accordingly and never look back,