If you haven't done a tune up in a while, that could be a good place to start.
You can inspect the ignition components for corrosion and wear. Even checking the spark at idle may help. It may be good enough for lower speed but not good enough for higher speed under load.
The accelerator pump should not be the problem if it exists at a sustained cruising speed. It may be the problem if it exists only when attempting to accelerate.
You can check the fuel pump volume by letting it pump fuel into a container of known size. I don't know what the spec for that should be - consult a shop manual.
Lawrenceville, GA