Criminal Law Questions? Ask a Criminal Lawyer.
The easiest way to get rid of an investigation like this is to get a defense attorney involved. Once have one, you most likely will never be charged.
He / she may also be able to help you get out of this without blowing in who ever actually made the call. (if this is a concern)
Talking to the police further on your own will not prevent a charge.
The problem is if you knew he was using a stolen ID number, and admit to the same, you facilitated a crime which makes you an accomplice and / or conspirator.
See a defense attorney ASAP.