BMW B58 OPF Decat Downpipe — 640i, 740i, 840i, M340i, 440i, 540i, Z4 M40i, Toyota Supra A90 GR
Unlock B58 performance with our 4.5 inch stainless steel decat downpipe engineered specifically for OPF/PPF models. Built from SS304 aircraft‑grade stainless steel and precision TIG welded with mandrel‑bent tubing, this BMW B58 OPF downpipe delivers faster turbo spool, sharper throttle response, noticeable power gains and a deeper, more aggressive exhaust note. Expect meaningful weight savings over the factory catalytic converter, reduced exhaust backpressure and improved cylinder charge for true real‑world results.
- SS304 aircraft‑grade stainless steel construction, TIG welded for strength and longevity
- Large‑bore, mandrel‑bent design for maximum gas flow and performance without sacrificing mid‑range torque
- Faster turbo spool and crisper throttle response for a more responsive drive
- Noticeable power gains and a louder, sportier B58 exhaust tone
- Lower exhaust temperatures and reduced backpressure to relieve the turbocharger
- Significant weight saving compared with the OEM catalytic converter
- Designed for BMW B58 OPF/PPF models only for correct fitment
We have installed and tested this B58 OPF decat downpipe ourselves and with customer cars, consistently seeing around 20–25 bhp gains, improved drivability and excellent fitment. Feedback from owners has been that it is very easy to fit.
Vehicle fitment — OPF/PPF models only
- BMW G20/G21 M340i 3.0L 285 kW / 374 PS — 2019 OPF
- BMW G22 440i 3.0L 285 kW / 387 PS — 2019 OPF
- BMW G30/G31 540i 3.0L 250 kW / 340 PS — 2018 OPF
- BMW G32 640i 3.0L 250 kW / 340 PS — 2018 OPF
- BMW G11/G12 740i 3.0L 240 kW / 326 PS — 2019 OPF
- BMW G14/G15/G16 840i 3.0L 250 kW / 340 PS — 2019 OPF
- BMW Z4 G29 M40i 3.0L 250 kW / 340 PS — 2019 OPF
- Toyota Supra MK5 A90 GR 3.0L 250 kW / 340 PS — 2019 OPF
OE cross‑reference: BMW part number 18329897313.
Installation notes
- Professional installation recommended. Tolerances can vary between exhausts and space can be tight.
- Swap the gasket at the turbo end of the downpipe. Failure to do so may cause a fuel smell in the cabin.
- We recommend adding a Lambda Sensor Spacer to help prevent an engine management light in most cases. Check our other items for spacers.
Want it fitted by experts? Book installation with Nforcd in Warwickshire. Request a quote: Sales@nforcd.com.
Why choose this BMW B58 OPF decat downpipe?
BMW B58 downpipe, BMW 640i downpipe, 740i downpipe, 840i downpipe, M340i downpipe, 440i downpipe, 540i downpipe, Z4 M40i downpipe and Toyota Supra A90 GR downpipe buyers choose this upgrade for proven power gains, stronger turbo response, aggressive exhaust sound, stainless steel durability and perfect OPF/PPF compatibility. It is a high‑flow, catless, mandrel‑bent, TIG‑welded SS304 performance downpipe designed to optimise flow, reduce backpressure and enhance the driving experience on OPF‑equipped B58 engines.