Okay.
You can't bypass the throttle set in place (or alter the configuration files in your equipment) from your ISP. Chances are this will get your service terminated. I know in the case of comcast they frequently check your modem, or in my case, the IP Gateway (Automated of course) for signs of tampering.
In the case of Comcast, they don't check shit and have no way to trace their modems back to you except by the MAC address that was registered to your account which can be spoofed. (it's a bit more, but that's generally the point).
You CAN bypass the throttle set in place, and alter the files in your equipment. Completely possible as I have done it before.
Chances are they will have no idea and won't terminate anyone service.. To be honest, even if they did notice someone "stealing" bandwidth, because of the way the "thief" goes about it, they can't figure out who's doing it unless they were to go door to door (process of elimination basically) and find the altered equipment. That's just because of the way their network is set up.. If you're in an apartment complex, you're practically home free since there's just a mess of splitters somewhere.
I wouldn't do this as others have said they can shut your internet off as they don't like people tampering with their systems, just stick with what you got.
Of course they would shut off your internet, if they could trace it back to you.. In order to bypass the throttling, you end up installing haxorware over the firmware of the modem which leaves them with no way to tell if it's theirs or not.
Well, suppose I would not get in trouble...I think I have an idea involving port forwarding...
Anyway, do you have a modem or just an RJ-45 wall socket?
AND, edited to show you proof I know what I'm talking about.. This is from the last time I successfully modded my modem.. 73mb/s on a RESIDENTIAL line.
This cable modem shit is crazy though.. A modded modem will give you free unthrottled internet on just about any cable line.