They're not special nuts -- it's just a bit awkward to get to them all. I put a blob of Blu-Tack up inside my 10 mm socket, then used that with an extension to remove the nuts. That way, I didn't lose the nut when it came off the end of the bolt.
However, removing the nuts is not really the tricky part. The tricky part is getting the ECU cover up and over the bolts, and out from under the carpet! This takes some manoeuvring, and it's worth making sure that the carpet is well and truly out of the way before trying to force the cover out from down there.
Good luck!