Cylinder pressure at 1500rpm is high, especially with the vanos system on this car. In general, low RPM is harsh on a motor since you can get really good cylinder fill and the motor is moving so slow that it sits at high pressures much longer. Knock is more prevalent at low RPM for this reason, etc. If you want to apply this to coils bmwfixerguy and his observations are correct you'll generally see them struggle at low and mid rpm first, it gets easier for them after torque peak but often lower RPM is still worse for misfires since mixes are leaner before torque peak. Lean AFR, high pressures (present and lingering at low rpm), e85, all these things make it harder to ignite. I think the notmpwr guy was confusing dwell and duty cycle for how hard the ignition system is working. That's true to an extent, but the coils have full dwell (charge time) at low duty cycles until 8,000+rpm, so they are fine from that perspective everywhere. It's a common misconception for people who started with old dizzy ignitions, since as rpm increases you lose a ton of charge time and get more misfires with a dizzy. Modern computer controlled ignitions don't have this issue until really, really high RPM. Since the coils are at 100% output from idle to redline, you will instead see them struggle down low every time. Multispark helps mask this and keep emissions clean, etc.