Here is what Norm Koerner found in testing his Viper with both headers:
http://www.viperalley.com/forum/vipe...gain-40-a.html
Here are more details about our product:
Hennessey Performance Engineering - Item Detail Page
A lot of people own the Bellanger system and are happy with it. So dont be offended by my comments if you have this system. Our system is more expensive than the mild steel Bellanger system due to the fact that stainless steel and the Burns collectors are very expensive. So I would just like to make the point that if you want a good header system and want something less expensive, call JonB who is Bellangers number one salesman. If you want the best quality along with the best performing system and dont mind paying a bit more, then give us a call. We can only build 1-2 systems per week, so we cant mass produce our system anyway.