Default Radio (3G) works better on OmniROM 4.4.4 than on my stock 4.1.2 - WHY??

Hello,

I recently installed OmniROM, but I missed the assistive cursor/pointer that is shown on the screen, so I can see where the "logical" pen tip actually touches.

So I'm back to the stock JB 4.1.2 ZTO - Brazil for a second round. I disabled most -- if not all -- bloatware and replaced TouchWiz launch screen with Google Now. I also installed Greenify, SetCPU and Xposed to trigger some actions or prevent Facebook from loading on startup.

Now, my only problem is the way the stock 4.1.2 handles 3G/HSDPA requests. On Facebook and in the built-in browser (which is basically an outdated version of AOSP browser) I constantly get timeouts, and the 3G becomes almost unusable -- except in near perfect conditions.

My question, in short is: how can I get the AOSP radio management flashed into my JB stock ROM? Is it possible? Are there workarounds?

Thanks in advance!