Phil,
The add header entry would just add elements to the soap request header. The question was related to HTTP header variables, I think.
On the inbound side, IS does not support use of soap request headers unless you write a custom soap rpc processor to do this. On the outbound side as long as you can build the message manually, you could add headers to a request message.
The web services connector wizard does not handle soap header elements described in a WSDL so any Flow it generates will not contain mappings to populate them.
Mark
#soa#API-Management#webMethods