please answer these questions:
- Is there any loss of power?
- Is there a CEL/Engine-Light?
- if Yes then what is the code?
[If you don't know the codes then go to Pep Boys or a small shop and have the codes read, then come back here and post them]
- Any other symptoms besides a sound?
- How long have you owned it?
- How long has the sound been happening?
- Where in CA are you located? (NorCal , SoCal ?)
That should be a good start.