Audible clicking at high speeds - what could it be?

I just recently started hearing an audible clicking sound in my 2015 Ford Mustang Ecoboost.

I only hear it in 3rd and 4th gear and only when I’m at about 3.5k rpm and higher. (I originally just thought my tires were kicking up rocks and it was hitting my car but then realized it was happening a lot).

I started using octane booster with my gas because I am stationed in Spain and not every gas station has premium fuel. I’m worried that this is a big issue and not sure if I can get warranty support here in Spain. The car has almost 26k miles on it.

Spain does not sell Mustangs so there is not much expertise here for the car. This mustang is a Roush edition and has the quad exhaust and a Roush cold air intake installed.

Any input would be greatly appreciated!