Grouping winston loggly output with tags?

I'm attempting to setup winston-loggly to handle performance logging in my app in addition to already handling normal errors/events etc. My logger setup:

var winston = require('winston');
require('winston-loggly');

winston.setLevels({ error: 0, warn: 1, info: 2, verbose: 3, debug: 4, silly: 5 });

winston.addColors({
  silly: 'magenta',
  verbose: 'cyan',
  debug: 'blue',
  info: 'green',
  warn: 'yellow',
  error: 'red'
});

winston.remove(winston.transports.Console);
winston.add(winston.transports.Console, {
  level: 'silly',
  prettyPrint: true,
  colorize: true,
  silent: false,
  timestamp: true
});



winston.add(winston.transports.Loggly, {
        token: "MY-TOKEN",
        subdomain: "MY-SUBDOMAIN",
        tags: ["Winston-NodeJS"],
        json:true
    });


module.exports.info = function(message, arg){
    winston.log('info',message, arg);
};

module.exports.error = function(message, arg){
    winston.log('error', message, arg);
};

module.exports.warn = function(message, arg){
    winston.log('warn', message, arg);
};

module.exports.debug = function(message, arg){
    winston.log('debug', message, arg);
};

module.exports.winston = winston;

And then to capture performance of each route, I've been using Morgan which I was able to pipe to loggly in my main app.js:

var theHTTPLog = morgan("dev", {
  "stream": {
    write: function(str) { 
      logger.info(str, null); 
    }
  }
});


app.use(theHTTPLog);

However this leaves morgan output polluting the same as normal app output. I'd like to tag all morgan output with "performance" when it's sent to loggly so that I can separate it and hopefully figure out a way to aggregate it to get statistics on how my routes are performing. How can I assign a tag at log time?

A better solution than tags is to create a custom log level for specific types of messages and log them at the new level.