Hi first time post but been dreading your post trying to figure out why my 91 LS is surging between 800 to 1100 RPM's ? I cleansed the trottle body and trottle sensor , checked for broken vacume lines . I put sea foam in the tank & new air filter . Gettin ready to replace the fuel filter today . It's a 91 with 200,000 miles on it . Also where is the vacume canister located at? Thanks Danny