Corrosion and the inner blocking through carbonids of the exhaust gases make a change after some time necessary to have the full power and reliability of the engine.
This special manifold, was invented in Germany and is a great piece for all Vespa GS 160, Rally 180 and SS 180 drivers.
With this conversion manifold you can adopt the exhausts of the 200cc+ Vespa class to the older models.
This way you can achieve better power with little to do.
The bracket at the traverse needs to be modified, depending on the exhaust you plan to use.