I'm pretty sure the STB is stretching the guide and there's no way to really prevent it from doing so.
When viewing an SD channel, the STB is outputting the video content at 4:3, but when you press the guide button it shows in 16:9 scretched across the screen.
I went into the settings and tried both options:
-If Auto Pillarbox is set to On it outputs SD channels in 4:3, but the guide is always stretched to 16:9
-If Auto Pillarbox is set to Off, SD channels are 16:9, but I can use the TV to show those channels in 4:3, which also brings the guide back down to 4:3. But HD channels which are 16:9 also have the stretched guide at 16:9.
It's been pretty annoying on a large screen reading text thats large and stretched wide.
On the 6416 it was ok, the STB outputted SD channels & the guide in 4:3, and HD channels at 16:9 (and pressing guide while on an HD channel would bring it up in 4:3)