"How do I back out the income sourced in NV from the W2 due to my residency in NV. "
Enter your W-2 as is. Then, on your part-year resident CA return, allocate to CA only the income you earned as a CA resident. This will result in a refund of any excess CA withholding.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
