I bought some Nano 168's which arrived yesterday to use on some random projects.
I tested one with a simple blink sketch and it seemed it was running half the speed it should have been. 
I checked on the sellers page and it said 16MHZ .
I checked the fuse and it was set to an external clock ( 8MHZ -> (FF)) and I can see the little crystal on pin 7/8 .
I checked with the seller and they said that there was a mistake and they are 8MHZ.. (kind of surprised they even understood ).
Anyway. I altered the clock for the board in boards.txt and uploaded the bootloader ( prior to yesterday I had never uploaded a bootloader or knew about the fuses!) .
Super, now I was getting a correct timing on the Blink sketch.
But now the serial monitor needs to be set at double the setting on the board
I tried a different bootloader the one named "ATmegaBOOT_168_pro_8MHz.hex"
Which reported to burn fine, but the Serial output is still half what the monitor sees
Any ideas? I have googled for hours to get this far and can't think what else to try..
Cheers
Rob
Arduino Nano w/ ATmega168-8
-------------------------
nano.menu.cpu.atmega168-8=ATmega168p8
nano.menu.cpu.atmega/ATmegaBOOT_168_atmega1280mega168p8.upload.maximum_size=14336
nano.menu.cpu.atmega168-8.upload.maximum_data_size=1024
nano.menu.cpu.atmega168-8.upload.speed=19200
nano.menu.cpu.atmega168-8.bootloader.low_fuses=0xff
nano.menu.cpu.atmega168-8.bootloader.high_fuses=0xdd
nano.menu.cpu.atmega168-8.bootloader.extended_fuses=0xF8
nano.menu.cpu.atmega168-8.bootloader.file=atmega/ATmegaBOOT_168_pro_8MHz.hex
nano.menu.cpu.atmega168-8.build.mcu=atmega168p
nano.build.f_cpu=8000000L