First off, I installed a
US Gear Unified Tow Brake into our 2006 Saturn Vue, not a Malibu. Iím sorry I donít have photos of an installation in a Malibu, but if you click here
you can see someone elseís installation who posted photos, however also not a Malibu. Secondly, I am somewhat familiar with your 06 Malibu, as I am a GM Technician, but different options will factor into your installation (e.g. power seats, electric power steering, engine size, etc.).
On our Vue, I installed the solenoid valve under the driverís seat and secured it with nylon zip ties to the seat track. Since our car does not have power seats, there was plenty of room to do this. Iím not sure if thereís enough room under the seat in your car. If you happen to have room, but have power seats that can be adjusted up and down, make sure that the seat bottom does not lower far enough to make contact with the solenoid valve if installed there.
I know you didnít ask about installing the cable and pulley, but what I did was route the cable through an existing hole in the carpet (where the seat base attaches to the floor at the left front of the seat), under the carpet, to the pulley. I had to cut out a rectangular section from the carpet underlayment/insulation to attach the pulley to the floor (CAUTION: Make sure there is nothing on the other side of the floor pan in the area where you mount the pulley such as fuel lines, brake lines, etc., that could be damaged by the screws that go through the floor.) I then sealed the screw ends with silicone sealer to prevent water intrusion. I also had to cut slits in both the carpeting and the floor mat to fit them around the cable coming up from the pulley so that it could attach to the brake pedal.
On our car, because there is an electric power steering motor and control unit to the left of the steering column, I had to install the control box up under the dash to the right of the steering column. I also secured it with zip ties. Thereís usually enough room under any vehicleís dashboard near the steering column to install a control box of this size. Iím not sure if your vehicle has a plastic cover panel under the steering column, but ours does, and I put the module above it so the panel hides it when reinstalled.
I donít like the idea of cutting additional holes in a firewall, so I routed the wires through an existing grommet for an electrical harness that passes through the firewall just to the left of where the steering shaft goes through. On our car I had several choices of grommets to use. I just used the one that was easiest to access on both sides of the firewall.
If you have more questions specific to your vehicle, I may be able to find the answers for you.