Twin Turbos are better for your V-style engines. There is no reason to have 2 turbos when you only have one exhaust manifold. Also, twin turbos are much harder to tune than a single turbo!!! and more expensive for the setup. Pointless on a fofo
You could run a twin turbo. Its deffinitely do-able. Its just, do you want spend more money on a twin turbo setup or less on a single and still get the same gains? If you were to go TT you would have the first streetable focus to my knowledge.
unless you wanna run crazy boost, its not needed cause w/ a TT setup, you use smaller turbos to prevent lag like said above. if you want to run a super high boost setup, then you can use twin turbos. for example, a 400 + whp beast wont start making good power till you get up top. but w/ 2 smaller turbos, you would have great power all the way through the power band!!