I've seen many instances like this on several 112 equipped vehicles. In the cases where the ECU was the problem, the mis-fires resulted in cylinder shut-down, which is unmistakable. There are two types of mis-fire codes possible. A given number of mis-fires per 1000 revolutions will set the fault code, but will not shut the cylinder down. A given number of mis-fires per 200 revolutions will result in cylinder shut-down because it can damage the cat. You didn't say which cylinders were mis-firing. If they're all on the same bank, and no cylinder shut-off occurs, you may just have a bad O2 sensor before the cat on the side that's affected. I've seen it happen a few times, usually on vehicles with 40,000+ miles. Good luck and let me know how it goes.