That's kind of worrying Luke. If everything is ok, those plugs should only be 0.8mm at the most after 10k miles.
What plugs are you running in it? (Make and type)
Which two were the largest? You've said #4 and i'm guessing #1 was the other with #3 a second choice. It sounds as if the two largest gaps were running lean - did those plugs have a whitish, glazed appearance?
Couple of things worth doing, compression test on all 4 pots, injector flow test on all 4, check injector "O" rings particularly where the injectors go into the manifold and check the manifold for corrosion at those points, check the inlet manifold gasket for leaks, also check all your valve clearances if anything is untoward in the previous tests.
Glad you've found the main symptom/cause of the rough running but what has caused it in such a short mileage?
