{"title":"Home page","description":null,"products":[{"product_id":"bmw-m340i-m440i-b58-downpipe","title":"BMW B58 Downpipe","description":"\u003cp\u003e\u003cstrong\u003eOne B58 downpipe that fits them all.\u003c\/strong\u003e 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.\u003c\/p\u003e\u003ch3\u003eFits every B58 car\u003c\/h3\u003e\u003cp\u003eCompatible with the \u003cstrong\u003eBMW 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)\u003c\/strong\u003e. 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.\u003c\/p\u003e\u003ch3\u003eWhy owners choose OKTAN\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFaster turbo spool \u0026amp; sharper throttle\u003c\/strong\u003e — lower back-pressure builds boost earlier.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDeeper, more aggressive tone\u003c\/strong\u003e — stronger note with no cabin drone at cruise.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnlocks your tune\u003c\/strong\u003e — removes the flow ceiling that caps Stage 2+.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTrue bolt-on\u003c\/strong\u003e — fits the OEM mounting points. No cutting, welding or fabrication.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003ePremium materials\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eT304 stainless steel\u003c\/strong\u003e, CNC-machined flanges, back-purged TIG welds.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM sensor positions retained\u003c\/strong\u003e — no extensions needed.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLifetime warranty\u003c\/strong\u003e against manufacturing defects.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eSpecifications\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eEngine:\u003c\/strong\u003e 3.0L turbo I6 (B58)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDiameter:\u003c\/strong\u003e 3.5\" \/ 89 mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e T304 stainless steel\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConfiguration:\u003c\/strong\u003e Catless or 200-cell high-flow\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFitment:\u003c\/strong\u003e Direct replacement, OEM mounting points\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cem\u003eMade to order, free tracked US shipping, dispatched in 10–14 days. Fitment confirmed before you buy — just ask.\u003c\/em\u003e\u003c\/p\u003e","brand":"OKTAN","offers":[{"title":"Catless","offer_id":48747998675189,"sku":"DP-B58-35","price":549.0,"currency_code":"USD","in_stock":true},{"title":"200 Cell High-Flow","offer_id":48748666913013,"sku":null,"price":669.0,"currency_code":"USD","in_stock":true},{"title":"Catless + Heat Shield","offer_id":48759639965941,"sku":null,"price":609.0,"currency_code":"USD","in_stock":true},{"title":"Catless + Install Kit","offer_id":48759639998709,"sku":null,"price":594.0,"currency_code":"USD","in_stock":true},{"title":"Catless + Heat Shield \u0026 Kit","offer_id":48759640031477,"sku":null,"price":654.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0818\/6868\/5557\/files\/Hf256cc6377ed40b19bc03d4c8e934c69d_4a85c4d2-f4ee-4132-9f38-5b6f8c78a80e.jpg?v=1787610604"}],"url":"https:\/\/oktanperformance.com\/collections\/frontpage.oembed","provider":"My Store","version":"1.0","type":"link"}