Buy 2 coil packs. Replace the bad one and keep a spare in the trunk. That's what I do with the m112s. Coil packs are not a performance degradation part. They either work or they don't and you'll know it when they don't.
No, they are definetely performance degradation part (unless BOSCH changed the coil pack design), and they are definetly not either good or bad, they do partially damaged without triggering a code, that's exactly what happens to my car.
I just bought the car with a bit lumpy idle (previous owner can't tell because they get used this small viberation at idle), changed the spark plug immediately but problem didn't solve, check all lead (only 3 years old), no damage, all of them have correct resistance as well (2+-0.2kohm). Since I already checked the vacuum, fuel etc, so the problem has to be coil pack.
There was no code and misfire counter indicate steady zero, and by using the crankshaft accelerometer I found cylinder 2 and 6 got partially damaged coil (one corroded conector, one good connector, it still fire up the cylinder but the spark is not as strong as it should be), also there were quite heavy carbon deposit on corresponding spark plug.
At beginning, I thought I can fix it by changing the coil on cylinder 2 and 6, but I was wrong. Yes, it fixed the problem at cylinder 2 and 6, also 80% of that mild rough idle went away, but the crankshaft accelerometer showing there were still randomly excessive roughness at other cylinder, since this didn't happens with partially damaged old coil, it clearly indicate other old but good coil somehow produce weaker ignition energy compare to new one and cause this imbalance, so in the end I changed all coils, and now it's idling like dream.
Yes, you can only replace the faulty coil, after I replace the faulty one, the rough idle is very very mild(my friend can't tell, but I did feel something), as I'm not comfortable with that, I changed all
