OTC (7667) GM Computer-Controlled Carburetor Tools Designed to adjust settings on computer controlled Rochester, Dual Jet, Quadra Jet, and VaraJet carburetors on carbureted GM engines 2 millimeters double-D - VaraJet lean authority screw and idle air bleed; and Dual Jet and Quadra Jet mixture control adjusting screw 2.5 millimeters hex - Dual Jet and Quadra Jet TPS adjusting screw 7 millimeters double-D - Dual Jet and Quadra Jet main metering jets 10 millimeters double-D - Dual Jet and Quadra Jet mixture control solenoid-rich screw