Obscure DTC P1371 P1373 P1313 P1314 codes

Now it's my turn on the misfire chapter. I describe hereby on my best asking you fellas some hints on possible causes (not the obvious ignition coils) and may this post help others in the future. Got all codes in a sudden after filling up Disco 96' tank with of course 93 octane fuel. Codes 1371 and 1373 are known as ignition coil early activation fault cyl 1 & 3. Codes 1313 and 1314 reflect the downstream effect on misfire catalyst damage fault banks 1 and 2. The trick comes from the 1371 & 1372, how come these two independent coils become defective at the same time! Cyl 1 and 6 are served from the same twin coil (it sparks by pairs as you may know), so if the cyl1 coil becomes faulty, the cyl 6 should immediately be affected too. Thus, I should get 1371 with 1376. If the logic prevails the same would be valid for cyl 2 and 3, codes and 1373 with 1372.:confused: This apparent paradox makes me believe the problem is somewhere else upstream the ignition coils. Am I missing something here? Does anybody have a clue on the possible real cause?