I believe that a X-pipe has a scavenging effect and I've been told that it will mellow out the tone of your exhaust too. It's nice to have one, but you don't NEED one. It's not hard or expensive to add a X or H pipe if you're still in the building stage. I bought my X-pipe on ebay for $45 and I'm going have it welded in when I put on my new mufflers and new headers. Good luck.