Innaccurate information, or help needed

I have a Lenovo ThinkPad Twist s230u that has a Broadcom 43228 that is
identified by the PCI ID of 14e4:4359.

I have attempted to use both the b43 and broadcom-wl drivers.
In both cases, the speed of my connection is about half of what it
should be. I have had this problem on Windows, but it was solved by
installing drivers from Lenovo's website.

The b43 page on the linux wireless wiki says that everything is
working as of kernel version 3.17, but there is obviously still a
problem or there is missing configuration information.

Any help would be greatly appreciated.

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Sayonara,
Burgess, Jonathan