Found at XDA by user sino8r - ppcg takes no credit for this!
Here is a handy guide on how to modify the ROM on your rooted phone so that your carrier doesn’t throttle your data!!!
sino8r stated at XDA that "
You need to have the SDK/adb plus drivers setup for this to work. There is no way of getting around this, so if you need help doing that... look somewhere else because there are numerous guides for that. Secondly, you need to make a backup via Nandroid of your current rom! I can't stress that enough! And finally, you need smali which is located here"
Step One:
Okay, find your current rom on your pc (the zip file) and open it with your favorite extractor (winrar is nice)(dictionary – I think 7zip is the best)
Step Two:
Go to the system/framework folder and extract services.jar file onto your desktop.
Step Three:pen services.jar and extract classes.dex to the desktop. Cut and paste classes.dex to your sdk/tools folder.
Step Four:
Now, download
smali and baksmali.jar from the link in the paragraph above. Rename them smali.jar and baksmail.jar for easier typing later. Cut and paste those two into the SDK/tools folder also.
Step Five:
Open your command prompt and cd (change directory) to sdk/tools folder. Then type this exactly (without the quotes: "java -jar baksmali.jar -o classout/ classes.dex". Look at your sdk/tool folder… that should have created a folder called classout. Open it until you find your files.
Step Six:
Locate the 7 files with "throttleservices" in the title. Delete them! Now type this into command prompt: "java -Xmx512M -jar smali.jar classout/ -o new-classes.dex". That should repack your edited files and create a file called new-classes.dex…
Step Seven:
Cut and paste the new-classes.dex to your desktop and rename it classes.dex.
Step Eight:
Open your services.jar (that should be on the desktop) with winrar (or whatever)(dictionary – again, try/use 7zip) and click add file. Add the classes.dex file from your desktop. It might ask you to replace it or save or not (it will depend on your extractor).
Step Nine:
After you edited your services.jar, copy and paste it to your tools folder. Connect your phone via usb cable to the pc.
Step Ten:
Boot into clockwork recovery. In the clockwork menu, make sure you go to mounts and storage and click mount /system before this next step.
Step Eleven:
Now, open the command prompt from your pc again, and cd to sdk/tools folder (if you are already there, you can skip this step! Good for you
).
Step Twelve:
Now type "adb push services.jar /system/framework/". Reboot your phone and enjoy! [sic]
DISCLAIMER
Nobody is responsible for destruction of your phone, boot loops, or cancellation/suspension of your contract due to excessive data use but yourself. Do this at your own risk!
ISSUES
The menu/settings/wireless & network settings/mobile networks are going to force close. It is rarely needed so this won't be a problem for 99% of users. Just make sure you have data roaming enabled before pushing your services.jar and that your APN is correct (which it should be already) because you won't be able to change those again. You can always push your old services.jar (from your rom.zip) to quick restore (way easier than Nandroid but whatever) Just do that the same way we copied and pasted services.jar to tools folder and adb push. ONE THING you might miss is having the option to use 2G only. To remedy this, just dial *#*#4635#*#* from the dialer. Go to phone info and select your prefferences... 2G only,3G only, or 3G preferred. There's an app for that called phone info by SC@taiwan on the market for free. It much handier than dialing all that *#*# crap. That should take care of most folks.