ORIGINAL: FOOPED
When I got my new DL-50 it also ran at 2500 on Idle and what they do at the factory is set the Idle stop screw. I removed the screw and sure enough the engine idled way down. Now I wonder if this is true on all the engines out of the box. I think so but its just my 2 cents worth.
Yes, the needles and idle stop screw are set to ensure the engines start up and run, that's it. You will always need to adjust them from there.