MBRP GMCA425 3" TURBO DOWN PIPE — CARB FOR 2001–EARLY 2004 GM SIERRA/SILVERADO 6.6L DURAMAX (LB7)

CARB-CERTIFIED PERFORMANCE FOR LB7 (2001–EARLY 2004): The MBRP GMCA425 3" Turbo Down Pipe replaces the restrictive factory LB7 downpipe to improve turbo spool, reduce EGTs, and sharpen throttle response — all while remaining emissions legal in California and all 50 states under CARB EO # D-763-2. Black-coated aluminized steel, mandrel-bent, and engineered for an easy bolt-on install.

• 3" mandrel-bent Armor BLK (black-coated aluminized steel)
• Direct-fit bolt-on design with required hardware
• CARB EO # D-763-2 (street legal where applicable)
• Backed by MBRP 3-Year warranty

Fitment

GM Duramax LB7 (2001–early 2004) only. Excludes mid-year 2004.5 LLY.

• 2001–2004 Chevrolet Silverado 2500HD / 3500 — 6.6L Duramax LB7
• 2001–2004 GMC Sierra 2500HD / 3500 — 6.6L Duramax LB7
• Model year note: Fits early 2004 (LB7); does not fit 2004.5 (LLY).

What’s Included

• MBRP 3" Turbo Down Pipe (black-coated aluminized steel)
• Installation hardware as supplied by MBRP

Cross-Reference / Alternatives (MBRP-only)

Looking to pair or consider an alternate MBRP system for your 2001–2004 LB7? Explore these in-stock MBRP items on CPP Diesel:

• MBRP S6005PLM — 4" downpipe-back, aluminized steel, no muffler (01–04 Duramax)
• MBRP S60210P — 5" downpipe-back, aluminized steel (01–04 Duramax)
• MBRP GMCA427 — 3" Turbo Down Pipe, CARB (2011–2015 LML) — same MBRP family for later platforms

Helpful Notes

• Verify engine code (LB7) and build date if your truck is a 2004 model year. 2004.5 LLY requires a different part.
• Re-use factory heat shields as applicable. Penetrating oil helps on high-mile hardware.

Yes. GMCA425 carries CARB Executive Order D-763-2, making it legal for use in California and other states that follow CARB regulations (when installed on listed applications).

It fits early 2004 LB7 trucks. It does not fit 2004.5 LLY. Check the VIN/engine tag or build date to confirm.

Users typically report quicker turbo spool, lower EGTs, and improved throttle response. Pairing with an MBRP downpipe-back system (e.g., S6005PLM 4" or S60210P 5") maximizes results.

Armor BLK (black-coated aluminized steel) for a clean, durable finish and great value.