Linerate : HTTP response modification

I have got it working.

"use strict";
var fpm = require('lrs/forwardProxyModule');
var os = require('os');
var proxyhost = os.hostname();
var processRequest = function(servReq, servResp, next){
    servReq.on('response', function processResponse(cliResp){
            cliResp.bindHeaders(servResp);
            servResp.setHeader("Server", proxyhost);
            cliResp.pipe(servResp);
            console.log('response modified');
    });
    next();
}
var createCallback = function(fp) {
    fp.on('request', processRequest);
};
fpm.on('exist', 'myForwardProxy', createCallback);

Curl from client. 'Server' is modified from 'Apache/2.2.22 (Debian)' to 'myLinerate'. It is placed in the end of response header. It actually looks removing and adding, instead of 'modifying'.

root@debian1:~ curl http://172.16.0.1 -v
* About to connect() to 172.16.0.1 port 80 (0)
*   Trying 172.16.0.1...
* connected
* Connected to 172.16.0.1 (172.16.0.1) port 80 (0)
> GET / HTTP/1.1
> User-Agent: curl/7.26.0
> Host: 172.16.0.1
> Accept: */*
> 
* additional stuff not fine transfer.c:1037: 0 0
* HTTP 1.1 or later with persistent connection, pipelining supported
< HTTP/1.1 200 OK
< Date: Mon, 02 Jun 2014 06:48:03 GMT
< Last-Modified: Tue, 27 May 2014 05:41:18 GMT
< ETag: "21a0a-c8-4fa5b251ef22b"
< Accept-Ranges: bytes
< Content-Length: 200
< Vary: Accept-Encoding
< Content-Type: text/html
< X-Pad: avoid browser bug
< Server: myLinerate
< 
It works! This is debian server 
This is the default web page for this server.
The web server software is running but no content has been added, yet.

* Connection 0 to host 172.16.0.1 left intact
* Closing connection 0
root@debian1:~ 

Without the script, it was...

< HTTP/1.1 200 OK
< Date: Mon, 02 Jun 2014 06:43:48 GMT
< Server: Apache/2.2.22 (Debian)
< Last-Modified: Tue, 27 May 2014 05:41:18 GMT
< ETag: "21a0a-c8-4fa5b251ef22b"
< Accept-Ranges: bytes
< Content-Length: 200
< Vary: Accept-Encoding
< Content-Type: text/html
< X-Pad: avoid browser bug
<