I've never worked on a Puch....but
Tony.... I think you're on the right track ..too much fuel
For a quick check.... run it with the air filter removed to see if it speeds up.. if it does.. then you need to buy a leaner jet.
I can't believe that price ($50 for 6 jets) .. take your jet out and read the number on it.. then e-mail one of the places mentioned here (moped warehouse?) and buy the next 2 smaller sizes.. they shouldn't be more than $2.50 apiece.
Till you try that.. you will just be guessing.
One thing you didn't mention was the spark plug color after running at top speed fpr 10 minutes.... do that.. if it is dark brown, its too rich.. it should be light brown.. but you have to run it wide open for a long time for the color to stabilize.