I wanted to thank you immensely Gardettes because I had the same problem and nothing works until I got to read your post here and did just as you said and managed to solve
Thank you again.
Use the AC66U Router and my printer and fast and instantaneous in print with official Firmware from ASUS now when I update to Firmware from ASUS Merlin the printer is extremely slow and each print takes approximately 2 minutes or more after the command.
This also happens with you or just me?