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Gutting a Miata manifold cat


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Thinking about shuffling around my points and getting rid of my header and use the stock manifold.


The stock manifold is terrible, has anyone gutted and converted a stock manifold to something better? Rules says after collector.

Seems like a competent welder could convert the stock manifold to a header


Here is a picture:



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6 hours ago, MMiskoe said:

If you want to use a stock manifold, why not just start with a non-california manifold where the cat is way downstream?



I had no clue that was the case! I got my car with the header already.


Alright problem solved :) thanks!


strange, I haven't find any pictures of what you are describing. Maybe onöy Californians buy OEM Miata manifolds...

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I know about it for two reasons - one was a friend running in a class requiring stock manifold took him a while to figure out why the other cars were so much faster.  Other was I had two cars, one crashed, one blown up/automatic and was doing a swap.  Had one of each sitting next to each other in the shop.  Needless to say the non-california car now has an O2 sensor that has no where to plug into.  Odd part is that both California cars ended up in NH.


The california header has one cat right up at the manifold, the second down in the tunnel after the OE manifold ends.  The non-california car only have the single one down in the tunnel area.

Edited by MMiskoe
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