In a way to really help, is the sound in any way connceted to the engine RPM ? Or is heard even with the engine off ?
If not related to the engine RPM, check your grounds, and all connections. It's there somewhere.
If related to the RPM of the engine; check for poor Ing wires, verify the coil condenser, alt, etc.
please let us know what you find
94 Mustang GT (cobra clone) 5.0 convertable, 5 sp CAI, Cobra intake, worked GT40 iron heads, 1.7RR, cat back, J4J1 ECU, 24 lb's, smog delete,
BBK LT headers, O/R X pipe, 70MM BBK TB, SCT custom chip. I think I'm done !!!