I remember a few years ago a back to back EH vs non EH test was done on Dudek's Hemi Challenger. The gain with EH was something like 4-5 hp, BUT testing showed the EH maifolds leaned out the motor slightly. After re-jetting the gain was more like 12-15. Still a pretty dang expensive 12-15 hp anyway you wanna look at it. Sounds like those guys need some competition in the marketplace.