Download this spreadsheet:
http://www.hoperf.com/upfile/RF22B%2023B%2031B%2042B%2043B%20Register%20Settings_RevB1-v5.xls
Use it to calculate the register settings for FIFO Mode (not PacketHeader+FIFO Mode).
Send those to the radio and see what data you get in. I hope that by using FIFO mode it will pass you the data as it arrives and not look for a packet header.