Resonated Test Pipes + O2 Defoulers | Fix P0420/P0430 CEL | G35 350Z G37 370Z VQ35HR VQ37VHR
If you’re running test pipes or high-flow cats on your VQ35DE, VQ35HR, or VQ37VHR and that dreaded P0420/P0430 check engine light won’t go away, this Resonated Test Pipes + Defouler combo is the proven fix for your G35, 350Z, G37, or 370Z HR, because deleting catalytic converters frees up massive exhaust flow and unlocks serious horsepower and throttle response, but it also pushes your secondary O2 sensors out of their expected range and triggers a CEL that kills remote start, hurts resale, and fails emissions, so these T304 stainless steel resonated test pipes replace the restrictive factory cats with straight-through 2.5” or 3” mandrel-bent piping for maximum scavenging and that aggressive VQ rasp while the built-in 12” resonators cut down on drone and rasp inside the cabin so you keep the exotic tone without the headache on the highway, and to solve the CEL issue every kit includes precision-machined 90-degree O2 defoulers with mini-catalyst inserts that space the downstream sensors out of the direct exhaust stream and filter the flow, tricking the ECU into seeing catalyst-level readings so the monitors set to “ready” and the light stays off without needing a tune, and the test pipes use 3/8” thick CNC flanges with OEM-style gaskets for a leak-free seal against your headers and Y-pipe, plus all hardware is included for a direct bolt-on install on 2003-2008 G35/350Z DE & HR and 2008-2015 G37/370Z, so you get the full performance and sound gains of a catless setup while keeping your dash clean, passing OBD2 readiness checks, and avoiding the limp mode or reduced power that comes with unresolved codes, making this the ideal solution for street-driven G/Z owners who want real gains, real sound, and zero check engine lights without having to drop money on a full ECU flash just to delete codes.
Key Features:
- CEL Fix for P0420/P0430 Codes: Includes 90-degree O2 defoulers with mini-catalyst inserts to space downstream sensors out of the exhaust stream. Tricks ECU into passing catalyst monitors and keeps your check engine light off without a tune.
- Resonated for Drone Control: Built-in 12” bottle resonators kill highway drone and excessive rasp while keeping the aggressive VQ tone. Get catless performance without the headache in the cabin.
- T304 Stainless Steel Construction: Mandrel-bent T304 stainless tubing resists rust, heat, and cracking. Built to handle track abuse, daily driving, and all weather conditions.
- True 2.5” or 3” Diameter: Choose 2.5” for N/A builds or 3” for boosted/fully built VQs. Increases exhaust flow and scavenging over restrictive OEM cats for real HP/TQ gains.
- CNC 3/8” Thick Flanges: Precision-cut flanges won’t warp under heat. Ensures a perfect, leak-free seal against your headers and Y-pipe/mid-pipe every time.
- Direct Bolt-On Fitment: Made for 2003-2008 G35/350Z DE & HR and 2008-2015 G37/370Z VQ35HR/VQ37VHR. Uses OEM mounting points and includes gaskets + hardware for easy install.
- Unlocks Exhaust Note: Deletes restrictive cats to unleash the raw, high-pitched VQ35/VQ37 exhaust note. Pairs perfectly with any catback for a true race-car sound.
- Maintains OBD2 Readiness: Defoulers allow secondary O2 monitors to set to “Ready” so you can pass emissions scans where only OBD2 plug-in checks are required.
- No ECU Tune Required: Mechanical CEL fix means you don’t have to buy an $800+ tune just to disable codes. Save money while still getting full catless performance.
- Restores Full Power: Eliminates limp mode or reduced power caused by catalyst efficiency codes. ECU runs normal fueling/timing maps so you get all the power you paid for.