Slow data speeds

Well,

I'm sorry that I can't exactly help your situation, But I can say that I am having a very similar issue. I am running D800 AT&T, CloudyStock V2.0 with dr87's Simple Kernel V5. Only have one APN, which the the Phone APN. Now, I do receive LTE, it also shows up on my phone as 4G.

I have also changed that lil bit in the Build.prop to my destination Country, which is US. But, anyway, After all of this I can only get maybe 2mbps downloads and if i'm lucky I will pull 1mbps upload.

I know for a fact that the LTE in my town is not that slow. I'm not really sure what is going on either.

Before I had CloudyStock on my G2 I could get around 11-12mps downloads with 4-5mbps uploads.

Sorry that I can't really help you out OP. I need help as well.

Since you mentioned, I have an AT&T with a T-mobile micro sim and the network signal (not data) has been very poor since I got the phone. Usually just 2 or 3 bars and completely lost the signal when I got down to the subway underground. I noticed that people were still using their phones while on the train so they could actually receive signals. I believe it's something to do with the sim but not for sure. I haven't had a chance to borrow anyone else's sim to try on mine so I couldn't really tell. I'm running CM 11 as well and I think the battery life has been reduced because of the weak network signal