Hey JD

You mention you definitely hear it from the rear of the vehicle (when the GF was driving it). So were you out of the car or in it with her?

Also, read this thread about a demon rattle:

https://www.crossfireforum.org/forum...verything.html

Even though he calls it a rattle, yours might be pronouncing itself as a chirp or peeping sound. You will see that he was pretty sure it wasn't in the exhaust system but it turns out it was. Might be something there.

RL