I have the same miss on my DL 50.. I checked my timing, it was at 33 degrees, so I set it to 28 degrees. The miss is alsmot gone - more of a burble ( ground running). I then put in the filed CM6 plug - what a difference, the engine even sounded different at idle and runs fine at high end.
Thanks for the tip!

We'll see how it does in the air.
cheers - ken k.