I have a GT- i9100 with a 4G plan (HSPA+). The problem is that I cannot get it to work on any non-stock rom. I have tried at least six stock roms and it has worked on each one. But whether aosp/aokp/miui, I can not use my data connection for internet. I have manually entered and double checked apn settings many times. I have enabled hsdpa etc under Galaxy/ Advanced settings and restarted many times. I have tried numerous modems to no avail. My phone is rooted but not unlocked. I am not sure if that is relevant. Help would be greatly appreciated.