you are putting it in to far. just pull it back about 1/2 inch and it should flow better. the nozzle is to close the the back of the filler neck and it backs up pressure on the nozzle.
This happened to me when I dropped the tank and broke the plastic thing on the end of my filler neck. I know you replaced it, but you may very well have damaged it putting the new one in. That is what regulates the pressure to the pump handle and tells it when it's full
you are putting it in to far. just pull it back about 1/2 inch and it should flow better. the nozzle is to close the the back of the filler neck and it backs up pressure on the nozzle.