Product Description
DIAMOND EYE K4120S is a 4.0" 409 stainless steel CAT-BACK exhaust system for 2004–2005 Chevy/GMC Silverado/Sierra 2500/3500 with the 6.6L LLY Duramax (all cab/bed). It delivers lower EGTs, a deep tone with the included muffler, and durable 16-gauge T409 stainless construction. The kit is engineered to bolt to factory locations and includes a turbo direct pipe section as specified by Diamond Eye for these model years.
FAQ: WILL THIS FIT MY LLY?
Yes—this system is designed for 2004–2005 Silverado/Sierra 2500/3500 HD with the 6.6L LLY Duramax, all cab and bed configurations. Always confirm model year and engine (LLY) before ordering.
FAQ: IS TUNING REQUIRED?
No. This is a bolt-on cat-back system that retains factory emissions equipment; no tuning is required.
FAQ: WHAT SOUND PROFILE SHOULD I EXPECT?
Touring-to-mellow performance tone thanks to the included Diamond Eye muffler—refined at cruise, authoritative under load.
Fitment Details
- Vehicle: 2004–2005 Chevrolet Silverado 2500HD/3500HD, 2004–2005 GMC Sierra 2500HD/3500HD
- Engine: 6.6L Duramax LLY
- Configuration: 4.0" single side exit (passenger side), cat-back, includes muffler
- Cab/Bed: All cab and bed lengths
Cross-Reference / Alternatives (MBRP-Only)
- MBRP S6000AL 4" CAT-BACK SINGLE SIDE (2001–2005 LB7/LLY) — aluminized alternative with similar sound/flow.
- MBRP GMAL413 Regular Cab Adapter (2001–2005 RC/LB) — useful if pairing MBRP systems with Regular Cab Long Box trucks.
Specifications
| Brand | Diamond Eye Performance |
|---|---|
| MPN | K4120S |
| Material | T409 stainless steel |
| System Type | Cat-Back, single side exit w/ muffler |
| Tubing Diameter | 4.0" |
| UPC | 841963121445 |
| GTIN | 0841963121445 (GTIN-12 / UPC-A) |
| Shipping Weight | ~65 lb (typical boxed) |
| Shipping Dimensions | 52" L × 21" W × 13" H (reference) |
| Prop 65 | WARNING: Cancer and Reproductive Harm — www.P65Warnings.ca.gov |
| Emissions Note | Cat-back; retains factory emissions equipment. |
