3 1/2" Turbo Intake Horn for 2001-2004 LB7 Duramax. Compatible with factory IHI Turbo or upgraded drop in IHI Turbos and OEM or aftermarket intakes. Great upgrade offering quicker spool up and more HP! Max-effort tuned trucks can see 10-15HP gains while applications with upgraded turbo's can experience as much as 20HP improvements. No tuning required.