Default [Q] how do i flash a modem through fastboot?

just as the title says. i want to know how to flash a modem.
i want to use the file that comes with my stock rom, not a zipped file.

i havent found this question for this phone.
so i might as well ask it.

i want to flash nexesque and then flash this to see if i get good signal and what not.
since flashing that and then a gsm patch didnt work so good for me.
is this possible or would it work?

and also would the modem work if i used a kit kat rom?

or if there is a thread with all the modems then please link me to it.
also i am on TELCEL Mexico just to mention.