It's really difficult to diagnose engine issues without actually seeing it. A few things associated with DLE engines that you may want to check. First is to replace the plug with a genuine NGK cm6 gapped to .020-.022. Make darned sure the plug cap is fully seated. Check to make sure the surface of the reed cage that the reeds seat up against are perfectly flat. Check the timing, I have read countless times about DLE engines having the timing off from the factory. The timing should be 28-30 degrees BTDC. IMO a good filter just prior to the carb is a must. Some guys will argue and give all sorts of justification to as why they don't run a filter on the airplane but bottom line is that is almost 20 years of running gassers I have never experience a failure related to using a filter, I have seen dozens of failures due to dirty carbs. The next is your fuel mix. For that engine a mix of 32:1 of just about any good quality AIR COOLED oil mixed with 87 octane is going to be the ticket.

As far as tuning goes, I usually set the high needle for close to peak RPM then come back and lean down the low just to the point that it won't transition out of idle, then open it just enough to get the transition back. This works well as a base ground tune. From there I listen to what it's doing in the air and adjust from there. As always you will get conflicting information, just weed through it and keep in mind where the information is coming from.