NA/NBSeller listing
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View listing at Mossmiata; opens in a new tabMiata · Buyer's guide
NA/NB Miata Oxygen Sensors, Manifolds and Catalytic-Converter Fitment
US-market 1990-1993 NA6, 1994-1997 NA8, 1999-2000 NB1, and 2001-2005 NB2. Split by OBD era, sensor position, federal/California emissions label, and exhaust layout. Mazdaspeed is excluded.
Current seller options
WHERE TO BUY
Open an exact listing, then confirm fitment, stock, price, and shipping with the seller before ordering.
Seller links checked . Prices and availability can change.
NA/NBSeller listing
Listed priceSee seller for current price
View listing at Mossmiata; opens in a new tabNA/NBSeller listing
Listed priceSee seller for current price
View listing at Good WIN Racing; opens in a new tabNA/NBSeller listing
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View listing at Good WIN Racing; opens in a new tabNA/NBSeller listing
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View listing at Flyin' Miata; opens in a new tabNA/NBSeller listing
Listed price$635
View listing at Magnaflow; opens in a new tabWhat you need to know
Separate NA6/NA8 and NB1/NB2, OBD-I/OBD-II, upstream/downstream position, and emissions label. The 1999-2000 California layout can include a primary converter at the manifold plus a downstream converter; 2001-2005 header/EGR/O2 layout differs. Mazdaspeed is excluded.
OEM numbers
Representative checked exact references include MagnaFlow federal 51597 and California 441771Mazda front oxygen sensor BP4X-18-861A-9Uand Moss product families 902-650 and 909-812. No universal converter or sensor number is claimed.Supersession
No OEM supersession chain is claimed. California converter legality is controlled by the exact current CARB Executive Order application and vehicle test group, not a generic cross-reference.
Fitment
Separate NA6/NA8 and NB1/NB2, OBD-I/OBD-II, upstream/downstream position, and emissions label. The 1999-2000 California layout can include a primary converter at the manifold plus a downstream converter; 2001-2005 header/EGR/O2 layout differs. Mazdaspeed is excluded.
Aftermarket options
Use an exact direct-fit sensor/converter only after checking emissions label, engine, position, and legal jurisdiction. Exhaust leaks can imitate sensor or catalyst faults; repair the failure cause before replacing a converter.
Before you buy
Emissions legality depends on registration state, underhood emissions label/test group, exact converter, and current law. Federal wording is not California approval. A seller cart is not guaranteed inventory, and no race header is presented as street legal.
Research and fitment sources
Supersede reviewed 12 unique research sources for this guide. 6 also appear above as a seller or official action and are not repeated here; 6 additional citations follow.
Research last verified .