I'm glad that the links I posted helped.
Here's an article about efi and Fedora:
I doubt if your motherboard had some kind of code affecting the boot. (anything is possible)
But if it does have some kind of code; think, what would a manufacturer have to gain buy doing that?
Most folks would just return the computer for a full refund.
You said;"It's frustrating that the cd can boot in efi mode" I feel for you- I am frustrated as well and running out of time and may have to return this Vaio to Sony because of this efi partition.
If we keep reading, looking, researching and keep plugging I believe that there is a solution to this. Or some way of getting this efi to comply with the kernel.
I'll continue to keep looking for answers and if I find one I'll post it for you.
I'm glad that what I have found has helped you some as I was concerned about that-
If you find the solution please post it.