I am proxying an API which returns headers that need to be transformed.
We're doing a rewrite of the proxy to work with node 0.10.x, also Im working on improve the examples for the new proxy.
I got an example for what you need here https://github.com/nodejitsu/node-http-proxy/blob/better-examples/examples/middleware/modifyResponse-middleware.js
If you got troubles or questions about that example, the discuss is here #520
I'm goona close this, if you got further doubts please open a new issue