This design has been superseded by this one.
Rebuilt the fan shroud to concentrate and extend airflow to the front of the nozzle. The shroud reaches into the fan to improve ducting to the exit.
Here's a contrast between old and new respectively:
It's a quick print and easy to install. It's a requirement that you print with a 0.4mm nozzle. The wall thicknesses are tuned for a single perimeter.
I also suggest to paint the seams accordingly. Seams are included in the 3MF as well as the gcode file.
The shroud fits well for me, inside the fan and on the extruder. It also extends a little forward of the fan. Let me know if you have any fit issues and I'll make updates.
The author remixed this model.
Extended the shroud towards the front. Added baffling to reach inside the blower.