I already posted this in the PN542 NFC Shield + FTDI forum:
I found out that SEL0 maps to PN532 pin 17 which is I1 and SEL1 maps to pin 16 that is I0.
That seems like a little error in the silk screen???
So I will try to leave SEL0 and put a solder blob on SEL1 when using the high speed uart connection.
For me it works but don't forget to send 0x55 and 30x 0x00 to get past the PN532 wake-up.
Hope this is of any use.

