Yeesh. So much arguing.
The gains on that header were dynoed against a Racing Beat on the same engine. Blue is the crazy header, red is the RB. This was not the final race tune, but it's a direct comparison.
Note that the engine was built to be reliable above everything else, thus no ITBs and with safe timing numbers on 91 octane gas. ITBs are great for throttle response (real throttle response) but they're a pain in the butt to deal with when you have a big cam and large altitude changes. This car is also set up to have a wide torque spread, and it raced with different cams than used in that dyno chart.
Here's the engine (in race spec) against a 1.6 Voodoo II. Dyno chart
. In this case, the naturally aspirated car would be faster
And actually, the Targa car is faster than any other Miata that has ever run on our local track. Period.
But more importantly, for the Targa Newfoundland, the rules penalize turbo Miatas pretty badly. I was running in the same class as rally-prepped Honda Civics. A turbo Miata would be in the same class as a factory rally EVO with a factory driver and a Group B quattro! So going N/A wasn't a difficult decision.
There are no plans to put that header into production. The amount of time involved would make it prohibitively expensive. It took me two months to design and build.