A question?, did you replace the fitting that came with the burner, if so it has the small opening needed to regulate the gas flow into the burner. Second is the air shutter disk on the front of the burner fully open?, if so close it most of the way and light the burner. Then at low fire level start to open it until just the tip of the flame is still yellow and the rest of the flame is blue. This is the point where the combustion is complete and the flow of hot gasses is the lowest which means the heat stays under the pot longer to do work.
If you have replaced the brass fitting on the burner inlet with one from a plumbing parts rack you need to use the original as the original has a small disk with a small opening to regulate gas flow into the burner. Without the disk the gas flow is way too much, 3'+ flames which are impressive but useless except for burning up the outside of the pot.