Describing soap header variables in WSDL is not well understood and generally not done in a standard way. I think it was for this reason, the IS web services connector wizard ignores soap header elements even if the WSDL contains them.
Per the soap spec, the WSDL should define a message part for each element in the soap header. You may have to inspect the WSDL manually or with your favorite WSDL editor (XML Spy Enterprise, CapeClear WSDL Editor, etc.) in order to determine the structure of the soap message header that SForce requires. It should be described as an element in the types section of the WSDL.
Create a documentType that conforms to that type, populate it and then add it to your subsequent soap requests using the pub.soap.utils:addHeader built-in service.
HTH,
Mark
#API-Management#webMethods#soa