To remove the restrictor you must take the exhaust off, remove the silencer/baffle, then cut open the exhaust body at the widest part. This can be done with a dremel metal cutter tool.
Once this is done, towards the rear of the exhaust before the bend, you will see a metal cone restricting the air flow of the exhaust. This cone must be taken out. There are 3 welds holding it in place. Taking it out can be done with the dremel tool again. Weld Once it is out, all you must do is properly weld the two parts back together, and put the silencer back on. Put that thing back on your moped and you should have a good 3-5 more mph's in your moped. Remember like always. UPJET UPJET UPJET and when in doubt, go rich.
[Edit] Having just finished this I would recommend anyone attempting this to be aware that it is not particularly easy and welding thin walled tubing can be a challenge as well. TIG (after lots of cleaning) was used in the picture above.
Original draft by Koh Schooley Revised by Marc Breitman