OKTAN
BMW B58 Downpipe
$549.00
Made to order — ships in 10–14 days
Fits your vehicle
Check fitment
Lower driver-side corner of the windscreen, the sticker in the driver’s door jamb, or your registration / insurance card. It’s 17 characters — we decode it instantly and never store it.
- Custom-made to order — ships in 10–14 days
- Free tracked shipping across the USA
- Secure payment
- Fitment guarantee — we confirm before you buy
Catless vs 200-cell — which configuration?
| Catless | 200-Cell High-Flow | |
|---|---|---|
| Airflow | Maximum | Excellent |
| Sound | Loudest, most aggressive | Aggressive, less raspy |
| Check-engine light | Needs a tune to clear | Usually code-free on a tune |
| Street & emissions | Off-road / competition only | Far more street-friendly |
| Best for | Track & max-power builds | Daily drivers wanting more |
Emissions & off-road notice. Catless configurations are sold for closed-course competition and off-road use only and are not legal for street use on pollution-controlled vehicles. You are responsible for compliance with the emissions laws where you drive. Prefer a street-friendly setup? Choose a 200-cell high-flow configuration above.
One B58 downpipe that fits them all. Our best-selling B58 upgrade is engineered around flow, TIG-welded from mandrel-bent 3.5" / 89 mm T304 stainless, and test-fitted in-house. It replaces the restrictive OEM catalyst for faster spool, a deeper tone and the headroom your tune needs.
Fits every B58 car
Compatible with the BMW M240i, M340i, M440i, 540i, 640i, 740i, 840i, X3 M40i, X4 M40i, X5 40i, X6 40i, X7 40i, Z4 M40i and the Toyota GR Supra A90 (2016–present). One downpipe fits the entire B58 range — it bolts to the factory mounting points. Cars fitted with a gasoline particulate filter (OPF, some 2018+) should choose the high-flow option; message us with your VIN if unsure.
Why owners choose OKTAN
- Faster turbo spool & sharper throttle — lower back-pressure builds boost earlier.
- Deeper, more aggressive tone — stronger note with no cabin drone at cruise.
- Unlocks your tune — removes the flow ceiling that caps Stage 2+.
- True bolt-on — fits the OEM mounting points. No cutting, welding or fabrication.
Premium materials
- T304 stainless steel, CNC-machined flanges, back-purged TIG welds.
- OEM sensor positions retained — no extensions needed.
- Lifetime warranty against manufacturing defects.
Specifications
- Engine: 3.0L turbo I6 (B58)
- Diameter: 3.5" / 89 mm
- Material: T304 stainless steel
- Configuration: Catless or 200-cell high-flow
- Fitment: Direct replacement, OEM mounting points
Made to order, free tracked US shipping, dispatched in 10–14 days. Fitment confirmed before you buy — just ask.
T304 StainlessAerospace-grade steel — never budget mild steel
True Bolt-OnFits the OEM mid-pipe — no cutting or welding
Flow-TestedEngineered & test-fitted in-house on real cars
Lifetime WarrantyCovered against manufacturing defects
Install at a glance
IntermediateDIY difficulty
2–4 hoursTypical time
Basic hand toolsSocket set & ratchet
Ramps or liftRaise & support safely
- Let the exhaust cool fully, then raise and support the car on stands or ramps.
- Soak the fasteners and O2 sensors with penetrating oil before removal.
- Transfer your O2 sensors to the new pipe — OEM sensor positions are retained.
- Seat the flange and tighten the V-band clamp evenly, then torque to spec.
- Running catless? Pair it with a supporting tune to manage fuel trims and the CEL.
- Every order is fitment-confirmed before it ships — stuck? We’ll walk you through it.
Complete the install
Customer reviews
4.9
/ 5
Verified purchase
Massive difference in turbo response and the sound is exactly what I wanted. Bolted straight up with no check engine light.
Verified purchase
Quality is well beyond what I expected at this price. Welds are clean and it sounds mean on cold start.
Verified purchase
Deep tone without any drone on the highway. Install was straightforward with the hardware kit.
Verified purchase
Exactly as described. The flange finish and sensor bung placement are OEM-perfect.