I would suggest going back to the fuel distributor for another look. If you didn't rebuild it, the item to look for is how free the "floating" piston is in the distribution block. It can't be worn, and can't be stuck or restricted in any way as the steel piston needs to responsively slide up and down as the revs change. It essentially floats between the force of air pressure of air entering the engine and the fuel pressure. I have three or four complete spare fuel distributors, and can take a picture of you didn't rebuild it yourself.
If you did rebuild it yourself, I'd still check again. The best of us can occasionally miss a spec of something getting into the system, and it doesn't take much to case trouble. I've encountered tiny particles from a cleaned fuel system still making their way through in the first flush.
I agree that the distributor is also working a look depending on what you have done. This model seems especially unhappy when the small plastic washers under the advance weight self destruct, or the little plastic covers on the spring posts crack away, causing an incorrect tension on the advance weight springs. You should be able to feel this at the rotor as there should be very limited play before there is tension when manualy turning the rotor. If there is significant free play, possibly the distributor should be overhauled. When I do this I end up with much smoother throttle response because the advance is closer to original. (Not that original is terribly good given the change in fuel, personally I decrease the spring free travel, making the mechanism "work" earlier).
Good luck with it, they are getting rare, but are good systems once you get on top of them. I'm also thinking of putting one into a 145.
