Milltek Resonated Secondary Cat Bypass For F80/F82/F83 BMW M3/M4

Milltek Resonated Cat Back Large-Bore Downpipe for BMW F80 M3 and F82 M4 (S55 engine). This resonated secondary catalyst delete is engineered for direct fitment to Milltek cat-back exhaust systems, combining increased flow capacity with refined sound character. The larger bore diameter reduces backpressure and improves scavenging efficiency compared to OEM units.

Fabricated from T304L stainless steel with mandrel-bent construction, this downpipe features a high-flow catalyst bypass design. Installation requires Stage 2 ECU remap for optimal tuning. Uses OEM hangers and mounting points—no modification required. Compatible with all Milltek cat-back systems for this platform.

Fits with Milltek Sport cat back only (Standard & Equal Length) and either Milltek Sport or OE primary downpipes

System Price

• T304L stainless steel construction
• Mandrel-bent, seamless bore
• Resonated design for refined exhaust note
• Secondary catalyst delete configuration
• Direct OEM+ fitment to Milltek cat-back exhausts
• Requires Stage 2 ECU remap
• S55 engine compatible

Milltek downpipes are developed and tested to deliver measurable power gains without compromising drivability or longevity.

Fits Milltek Cat-Back.