Node load balancer using http proxy slower than original server

I have a web service built in delphi and I built a load balancer using node-http-proxy module for scaling the webservice.

When I'm receiving a lot of requests (using Jmeter with 100 threads) I lost performance. If make a request to the port of the original webservice it responds too much faster than when a I make the same request for the node load balancer's port.

I've tried to set maxSockets = 10000

var agent = new http.Agent();
agent.maxSockets = 10000;
var proxy = httpProxy.createProxyServer({aget: agent});

and I've tried it too

  var agent = new http.Agent();
  agent.maxSockets = 10000;
  proxy.web(req, res, { 
    target: {
        host: server.host,
        port: server.port
      },
      agent: agent
    });

but the problems still exists

I thought to use the node clusters but there's a bug when using windows. This one, and I can't find the files they tell to edit to fix the bug.

Does someone have any idea that I can apply?