Stamina training, get plenty of hard day’s riding in cos that’s more or less what you will be doing if you factor in the practice sesh before the race and if you’ve got long transitions between the stags with long climbs, you’ll burn yourself out for the timed stages when the speed counts, I discovered that a few weeks ago! Lots of stand up peddling and short fast bursts, see if you can get out with some hardcore CX riders to train with.
I joined a gym to use at lunchtimes, also started jogging as well as commuting to work on my road bike, plus the usual weekend riding at the trails (which all helpled) but it was too little too late, think my other downfall was also not fuelling up during the day between the practice and the race and having time to rest between.
Good Luck, just enjoy it.