The main restriction in the E9x M3 exhaust is the primary cat. The ACM test pipes are designed to replace the primary cat with perfectly mandrel bent, top quality pipe which retains OEM o2 sensor bung locations and bolt directly to OEM exhaust manifolds. The rear section of the pipes can either be clamped or welded on for a factory-like fit.
*ECU software or module is required to keep the check engine light off*
*These are for off-road use only as deleting catalyst is not legal in all 50 states*