Runs much better, BUT it still has the stumble if you get on it too fast. No idea if it's a lean stumble or a rich stumble. Nor do I have any idea how to fix it.
First thing to try might be to see if you're too rich or lean on acceleration. Try changing the position of the accelerator pump rod. There are 2 holes on the lever, the outside one (where the pic shows yours now) provides the least amount of fuel, inside more fuel (increases the accelerator pump piston stroke).