When coming almost to a complete stop my 2001 Bullitt sporatically tends to idle surge while emitting a low pitch sound. Any ideas?

 

Check all connections on your intake from your filter to the throttle body and be sure they're leak proof(air tight). I would also check your IAC valve, possibly clean it out. I had this same problem and have almost completely alleviated it by doing these things. Here's a very very basic video for IAC.

 

classic egr symptom. sounds like it's sticking open.