WARNING: This page is about a different car, the 2003 GMC Sonoma and 2003 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Lower Engine Noise, Regardless Of Engine Speed - Diagnostic Table (1 Of 2)
Courtesy of GENERAL MOTORS CORP.
Fig 2: Lower Engine Noise, Regardless of Engine Speed - Diagnostic Table (2 Of 2)