HiCustomer The Impala has 2 different motors that it could have in it. I am sending you information on both, the first one is the 3.4L version and the regulator is mounted to the fuel rail.
Caution: Connect the fuel return line before tightening the regulator attaching screw in order to prevent the regulator from rotating. Rotation of the regulator could damage the retainer and spacer bracket and lead to a fuel leak at the regulator inlet.
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Tighten Tighten the engine fuel return pipe nut to 17 N·m (13 lb ft).
Tighten Tighten the screw to 8.5 N·m (75 lb in).
THE NEXT ONE IS THE 3.8L MOTOR. Thanks
Important: Always maintain cleanliness when servicing fuel system components.