“For state income tax purposes I'm now considered a CA resident, as well as a PA resident, and am filing returns in both states. “====I guess you can be both part year res of PA and part year res of CA but you can’t be a full year res for both CA and PA; I mean as long as you move from one state to another state during the year, you are a part year res for both of the states.
“Most of my income which is taxed by PA (interest, dividends, mutual fund capital gains) is also taxed by CA. “===============No I don’t t hink so; you are NOT subject to double taxation. I mean as there is no Reciprocal Agreement between CA and PA, you, as a nonresident of CA need to pay tax to PA and also need to file your CA return as a full year res of CA( as I assume that you are a full year res of CA) to claim your tax paid to PA on your CA return.
“Can I include the PA income taxes in my CA itemized deductions?”=========As mentioned above; as long as you pay tax on your income earned in PA to PA, you need to claim it on your CA return.