In case anyone is interested, I have run brand new monark 265 nozzles for about 1k miles, then tried new monark 314's in my om603. I have noticed slightly less smoke at full throttle, but barely noticeable. I have been unable to detect a difference in the idle, power and sound level. In the future I would recommend using these nozzles as they are the latest design and dont have any adverse effects, but only if you are planning on buying new nozzles anyway or else the difference is not worth it.