If you don't want to eliminate the 1st catalyzer with your new aftermarket header, this is the option for you. You should have less problem on the emission test, and the manufacturer say that you should gain 12whp in 2th and 3th gear if you have also the PPE midpipe.
Here the product link.
A little feedback from a Miata.net user (Suprajayaz):
"Since this project was initiated for autocross, I wanted 2nd and 3rd
gear data since these gears are most relevant to autocross use. There
was an increase of ~ 12hp in both 2nd and 3rd gear and > 9hp in 4th
gear. My baseline (green line) is AEM intake with piping/filter behind the bumper to be STR/CSP legal + a Roadstersport Race muffler. The red line is changing the stock mid-pipe to the new 2.5" STR/49 state legal catted mid-pipe while the top blue line adds the new STR / 49 state legal, catted header.
You can see both the HP and torque increase is across the full rpm
range with almost equal shaped graph lines, which helps validate that
similar conditions were used for each run. Below is a summary of the
data.
4th gear max gain: + 9.16hp (+6.5%), + 6.46ft-lbs (+ 5.0%)
3rd gear max gain: + 11.96hp (+8.7%), + 6.57ft-lbs (+5.2%)
2nd gear max gain: + 11.92hp (+9.1%), + 3.99ft-lbs (+3.4%)
What one does not see in all the data is the increase in throttle responsiveness. Throttle application is much more apparant and almost feels like having a lightened flywheel such as used in the 2006 MX-5 that won the 2008 SCCA National Championship in CSP that I co-drove. In summary, the new header + mid-pipe made positive results in both HP and torque while meeting the SCCA ST ruleset."
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| 2nd Gear |
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| 3rd Gear |
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| 4th Gear |
