Just a reminder: I have seen the engineering comparison between the headers designed for the 5.7L hemi and the exhaust ports on the 6.1L. Those headers shroud about 10% of the exhaust ports. The new version will not shroud any of the exhaust port. That may account for a significant difference, but we'll have to wait a few weeks for definitive results. My car is being used for measurements this week, and I believe the holdup will be tooling.John Hennessey said: