[T-Mobile LG G2x] DsturbD:
UPDATE 6-15-2012: i just wanted to update the beginning of this post to make it a little clearer, the original text is below

to get the v21y base band on your phone over the air, you have to go back to stock

to do this you need a stock rom, either your own backup or the one from this thread

http://xdaforums.com/showthread.php?t=1248644 (the first and second link is a stock 2.3.3 nandroid which is a zip you extract on your pc and run flash.bat from inside that folder)

if you need the drivers, download the third link.

follow the steps in that thread, it works

if you have your own stock nandroid, just boot into ClockworkMod Recovery and restore it (after you backup whats on your phone now)

then reboot your phone

after restoring either your stock nandroid or the one from the post above, shut your phone off and remove the battery and use NVFlash to restore the stock recovery

http://xdaforums.com/showthread.php?t=1056847

reboot your phone

now that you have your phone like it was from the beginning you can go to System Settings/About Phone and click on Software Update. this should pull down the updated Gingerbread version 2.3.4 and the new baseband v21y. IT WILL OVERWRITE YOUR PHONE AND WILL BE PLAIN STOCK

it takes a few minutes so be patient

once it is done and it rebooted your phone you will have to put ClockworkMod Recovery back on it using NVFlash. then you can flash other roms to your phone

please keep in mind that there is a bluetooth issue with both GB and ICS roms on this baseband and that only a few roms actually support v21y. Owain has written an update file that you flash to get support on any rom with v21y, supposedly it does work on any rom (GB or ICS) but i have not tested it, so read up and test if you want.

as of CM7 RC3 all CM7 builds support v21y

please thank the owners of the threads linked above, their methods worked flawlessly for me and i hope they work for you as well. this was a very easy way for me to get the new baseband. good luck!

original post------------------------------------------------------------------------

i was having a heck of a time trying to get the new baseband installed on my phone. i had all the stuff downloaded and all the instructions ready, had the KDZ file, the LG tool, everything...but i could not get anything to work

so what did work?

well using CWM Recovery i restored my stock backup i had made when i first got the phone (best to save this off the phone as well in a safe place) and then using NVFlash i put the stock recovery back on it

once that was done and i was booted back into stock you can go into the About Phone and choose Software Update (or whatever its called) and check for an update. it found one and proceeded to download a 30meg file. asked if i wanted to apply the update, installed it, and rebooted into a nice shiny new 2.3.4 GB setup with v21y and the new baseband installed!

the CM7 nightly build (June 3) is working great. getting ready to try a couple of others (Buru, EB, Genesis (although i was having a problem there, see that thread))

so its only been one day on it but so far calls are good, gps lock is fast, overall loving my phone even more than before!!