wait140485 and Ginnu
Well I also had the same question and nobody could answer positively, even Immigration Office at CSC.
I have similar situation, I-485 pending and wanted to file AP. Everybody says send it to CSC where my I-485 is pending. But what is the PO Box? The customer service representative did not have answer and connected me to Immigration Officer. She was also baffled. And finallly she advised me to send it to PO BOx 10485 (Attention I-131).
Guess what?? I sent it and INS received about 10 days back. Still my check has not been cleared and no receipt...