I've owned several one piece exhausts during my time with the Fizzie (the one we know here in DK as 5.3hp exhaust with 32mm downpipe)
They work ok, earlier versions seems to work better than the new crap you can buy cheap from "Protuna" and others..
I don't know exactly what or where the difference is, but the old one piece exhaust revved higher and had a decent bottom end.
But, what i do know, is that if you can manage to get the restrictor pipe out of the two-piece exhaust, and remove the 1'st exhaust baffle inside, and shorten the little muffler pipe/thingie accordingly, it will outperform both the 5.3hp exhaust and even the good old 8.5hp straight cut exhaust. Even with the 28mm downpipe.
As long as you dont push it to hard with big bore cylinders. They tend to overheat because the exhaust flow is a little more restricted with the 2piece exhaust.
I don't know if there is any difference between the Danish street legal exhaust, and the ones sold in other countries.
Don't blame me, if it won't work for you.
Hvis ikke du har tid til at lave det rigtigt, hvornår har du så tid til at lave det om ?