I think I have fixed mine finally. 4 days with no flashing cel.

Although my plugs were only a year old done by the previous owner, after replacing everything possible just like you have I decided to try two new coils on the cyl 1 & 2 which were the only consistent misfires codes I got from random misfires.

Since replacing those two it's been running good.

Maybe they were faulty or went bad when the valve stem seals were leaking fouling the plugs.

Through my research the coils are pretty sensitive and even dropping them on the floor can damage them.

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2005 Imola 4.8iS