This engine is my first gas engine experience, so I don't know if I have an engine problem or just set up and tuning needed.
This engine is new, and has been ran on a stand for about 15 minutes, and ran on the plane for about 45 minutes. The engine has started easily and seems to run fine with good acceleration. The only problem is I cannot get the idle down. With the throttle all the way to the stop, the engine still has a good pull on my 4 Star 120. I don't think it could get airborn, but it would taxi very fast.
Here is what I have for setup.

The idle stop screw has been removed.
The throttle return spring has been unhooked and inactivated.
I'm using an APC 16x8 prop.
Using high octane noethonal fuel with 32-1 mix Still HP Ultra oil per VVRC recommendations.
I have not touched the original settings of the high and low speed needles.
I've checked my throttle servo to make sure it is closing the throttle enough, and it is hitting the stop causing a slight bow in throttle linkage.

I do not know how Walbro carburetors work, but I was expecting to see the engine to quit like a glow engine when at that point.
Would appreciate any help and advice on the matter.
Thanks
Lamar