The natural metal tube is hooked to the air cleaner and supplies a clean air source, the vacuum inside the choke module pulls the clean air down into the exhaust manifold where it is heated by the heat exchanger inside the manifold and is then drawn into the choke module through the insulated tube to heat the spring.

Most of the choke parts are available on e-bay.

http://www.ebay.com/sch/i.html?_from=R40...amp;_sacat=6000