http://www.hennesseyperformance.com/...mance/Dyno.php
We got these numbers running through the stock exhaust system from behind the mufflers. I think there would be a bit more power with a larger diameter exhaust system. Anyway, we will try to get it to the track at some point soon. Though I am not sure how well a 5300 lb. truck is going to do in 95 deg. heat even with 538 rw hp. We will let you know.