Code P0660, Intake manifold tuning valve location needed

The actual valves are controlled by the vacuum actuators in the first image. The VIS that throsw the code is the Variable Solenoind you mentioned, but there are 2, the code you have is set by the VIS #1 solenoid, it's on the right side of the engine toward the under the engine cover. The code is set if the PCM detects no signal voltage changes when it tries to activate the valve for 2 drive cycles.
The common reasons for this are the solenoid has failed, the connection is bad or there is a short or open in the wiring. For testing there are a couple of options. Use a VOM to test the resistance of the solenoid it should be between 29 and 35 ohms. Then use the volt meter to check that there is full battery voltage in the connector on the Red wire. The Orange wire goes back to the PCM and is a pulse width modulated ground. I believe it uses the same solenoid for both units so you could measure both to compare the resistance. Both solenoids also get power from the same feed so if one has it but the other doesn't then it has a bad wire. You could even swap the solenoids to see if the code changes but testing should show the problem.