After you file

Can I amend my return without a W-2 C? I have no way of requesting a corrected W-2 from my employer, and management just tells me 'corporate knows there's a problem'. But by looking at paystubs, I was able to confirm where the error was and I know the the only change I need to make is to make the state income the same number as the federal income. Can I submit an amendment without additional documents or am I just stuck in limbo here without additional paperwork from my employer?