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I am not sure how much you are going to like this answer. CA enforces the standing that because they receive their income information about taxpayers from third parties (banks, employers...) the taxpayer has the ability to contact these third party reporters and dispute the items directly.
CA places the burden of proof on the taxpayer to show that the information is not correct. If you wish to dispute the income then you will need to respond to the notice sent to you within the time frame requested in the notice.
If you left CA in 1992 you will need to find someway to prove that you left prior to 1993 perhaps you have something. When were you employed by the company where you currently work? If you are with the same company they will have your information still on file. If you worked for a different company then they would be worth contacting.
I wish I could tell you something simple but CA is strict on their guidelines.