Router Asus RT-N16 is supported by the tomato?
Firmaware What should I use?
There's manual to upgrade?
This is as close to a manual You will get» http://tomatousb.org/tut:installing-on-asus-rt-n16
well you have to use build K26USB MIPS2
install first ddwrt and then flash tomato or install tomato directly using asus firmware restoration software (is on CD)
As Shibby20 mentions there are two ways to install Tomato on the RT-N16.
1) The "official" method described here: http://tomatousb.org/tut:installing-on-asus-rt-n16
2) The method described here: http://tomatousb.org/forum/t-251656/installing-on-rt-n16#post-992768 which involves flashing to an intermediate build of DD-WRT then to Tomato. The advantage is that you don't need to use the Asus firmware utility, which has been the source of some problems for people.
Which tomato usb build is good for Asus RT-N16 ?
"Good" is rather subjective. One man's meat is another man's poison.
There is a third way.
3) Using tftp, which needs neither ASUS CD nor DD-WRT nor Microsoft products.