[T-Mobile, Samsung Galaxy SIII] Psychotic-Cerebellum:
Not sure what caused this or what exactly the problem is so I'll try to include everything about the issue and everything I've tried to correct it. Anyone who can help you will hereby earn my undying gratitude, rights to my soul (may not be much of it left but whatever hasn't been sold or lost, all yours ;)), and as if that wasn't enough, a modest Christmas (or belated Christmas) donation if anyone can actually abolish the issue. That being said here's what's up:

All started a few weeks ago, like I said not sure what caused the issue so I'll just list everything I did. I flashed a bunch of ROMs, Frosty, Jedi Invasion, Free GS3, and probably a couple more I can't remember. I also was trying to see if maybe I could get better reception at work and better data speeds overall. So I downloaded a bunch of modems from DocHoliday's T999 Modem thread and flashed a few, settled on UVDLJA as it gave me the best service. I also downloaded his aroma modem flasher after that but then still ended up using the afore mentioned modem. I also used his build.prop tweaks. Here's what I changed:

HSXPA= 3

HSDPA= 6

HSUPA= 24

GPRSCLASS= 12

After the modem switch and the tweaks I was getting unbelievable speeds (for me at least). I went from like

7.5mbps

download and

1.2mbps

upload to

24mbps

upload and

2mbps

upload. Now flash forward to tomorrow and I flash back an forth between I think Free GS3 and Frosty (applying the build.prop edits every time I switch) and maybe something else and then later on I realize that my data is acting strange. It seems to not kick on. I have to hit stop and refresh a few times and then it clicks on and loads fine. I try to speed test same thing. I try to play a YouTube video, it only plays for like 30 seconds, stalls, goes, stalls, then doesn't start back up. However, I tried to download a new ROM and it dls at like 1mb/s the whole time after taking around a minute to start. The problems gets to where every other time I use my data this occurs. So, I switch ROMs multiple times, no build.prop edits done, same thing. The Jedi Invasion ROM worked better than the rest, for some reason unknown to me, but the issue still occurs. I re flashed all kinds of modems, no solution. Tried the Paranoid Android ROM cuz I wanted to try it. Data hardly ever worked on that. Would get stuck on 3g and didn't like to change to H+. Worked sometimes, but more often, not. Flashed to Wicked v3 and it worked pretty good, but after the v5 update its almost as bad as Paranoid Android. I even tried wiping my data, stupidly I did this before restoring my original nandroid backup, and even noobier erased all my nandroida when formatting data thus loosing it. So basically that's it.

Not familiar with apn's, vpn's, or for that matter much of anything complex either. Like I said though ANY help would be incredibly appreciated. I tried posting in DocHoliday's post but got no response. Also mentioned it in the Paranoid Android thread since that ROM was insanely hazardous to my data. Also mentioned it in the Wicked thread after the v5 update crippled me. Hoping for my Christmas miracle here. Thanks in advance to anyone who replies and Merry Christmas to all!