Detectives appealed for mobile phone and dashcam video of a black Mercedes and a black Jaguar seen at the end of last month in Ayrshire.
The cars are known to have been on the A714 road from Girvan to Newton Stewart - the Mercedes on Monday, 29 April 29 and the Jaguar on Tuesday, April 30.
A man has been charged with the murder of Ms Faulds, who was aged 39 and from Kilmarnock, Ayrshire. She was last seen alive on April 28 in Monkton.
Ross Willox, 39, made no plea at Ayr Sheriff Court and was remanded in custody.
Detective Chief Inspector Martin Fergus, who is leading the police inquiry, said: “What Emma’s family is going through is unimaginable and our priority is to find her.
“I am thankful to members of the public who have been in touch and have provided us with valuable information which has led us to explore this area.
“I believe the A714 route is key to helping us find Emma and I am appealing again to those who use this route regularly, please take time to think back and consider if you saw a Mercedes or Jaguar car on this road or parked up somewhere, or even off road.
“If you have dash cam footage, please take the time to go through and check it.”
He added: “You may not realise it but you could have captured footage of the vehicles in these locations which could provide us with vital information and assist us in finding Emma.”