Son this is no way to fix a problem. The gap in the distributor is not what "fixed" this. What you had or have somewhere is an air leak. Period. There is only one way to get high RPM. That is an air leak. That air leak can be anywhere, including through the carburetor. Regardless of timing or mixture, the reason an engine runs at higher RPM is air into the engine. It might be as simple as (pull out of the blue) stuck/ misaligned/ etc secondary throttle blades. Might be the carb body is loose on the throttle plate.
What you have done here is changed "something" and you and I know not what, which changed the problem.
