I know for a fact that I've downloaded much higher than 20mbps, and at my old house when I was on their 8/2 plan I was still downloading at similar speeds as I am now, which is why I figured their speeds were supposed to be in bytes.
Yea, powerboost is still glitchy for most ISP. It's all pretty complicated (even I don't understand it 100% and I should) but try not to think of speed as Mbps. Instead think of it like moving from one house to another. A Mbps is like one day worth of move. In reality, that day is made up of tons of little tiny trips. Some bigger, some quicker, some not even moving stuff, but just used to organize the whole thing. When a transfer occurs, it's given a session ID. The MTS(system in your ISP) monitors that session ID ans tries to limit/control/etc the traffic. Its not so much a speed dial they can turn up or down, but rather integrated into the way they are using DOCSIS, the system behind how cable modems work. So when you first start a session, you can get much higher speeds per frame then set by your modem's configuration file, so as the session goes on (usually a second or two) it forces a idle, or a handicap on the traffic to confine it to the restrictions placed upon by the modem's configuration file(that is determines by your internet tier). Where it gets complicated is with powerboost and DOCSIS 3. Powerboost, or what ever proprietary term your ISP calls it, can adjust the restrictions places upon certain session ID's based on the available bandwidth in the area. It's only supposed to work on single sessions, to give you the first couple of seconds of extra speed to say, buffer a HD movie stream. In torrent downloads, which have seeds to multiple clients, your getting multiple sessions (aka Multicast I think) so that speed boost can be amplified. Then you have DOCSIS 3.0, and the session system kind of breaks down there, because the CMTS isn't fully designed to track which sessions belong to which modem. In practicably terms, this means, if you have 10Mb down, and speedboost allows up to 12, and your bonding on 4 downstream channels of your DOCSIS 3, you could a almost 100% speed increase. Now like I said before, that speed increase isn't permanent, so it gives you a connection that goes fast, then slow, then fast, then slow. I am sure you have seen this with speed tests. Where it goes way up, then down a bit, then up. Or it goes up, and then slowly down, making the test take a long time. This kind of traffic management can cause issues, I am sure you can imagine, with real time games. Also, keep in mind, their is some inacurcy in this description of DOCSIS, because A, I don't 100% understand it(I am not a engineer), and B, I wanted to keep it within the scope of this post. Thought it might help for you to understand some of what is going on in the background.
Here is what I suggest:
1. Try
this test. Not only is it one of the more accurate ones, but the support for it really helps you understand it's results. Look at the capicity vs the speed: Capacity (of about speed). Look at the QoS. Look at your TCP graph. Compare before and during particular bad lag. Look at your forced idle and the max pause between frames. All these things are going to give you clues, **assuming this has anything to do with your ISP**. It could be the servers, like everyone is saying. Even though the game is P2P, it still needs the server as a conduit. Just like a PS3 game might be P2P, but PSN still needs to be up to work. Also, it could be the backbone throttling P2P traffic between your ISP and the servers, and your friend's ISP is working on another backbone. I have seen that alot, and besides changing ISP, there isn't a whole lot you can do. And even then it might still not help, because it could be about where you live and a common peer used by all providers in that area, and you friend happens to live close to a different peering backbone. So yea..it's all very complicated. Hope my info helps a bit.