Test the max flow rate of your K1 / K1 Max using the pre-sliced GCode.
DO NOT USE THE STL!!! It's just a dummy required for uploading the GCode.
INSTEAD DOWNLOAD it from here: https://github.com/3DPrintingGeek/STL_Files/blob/main/Calibration/Creality_K1_and_Max/Max-flowrate-test-20-34-230-220-K1.gcode
The test based on the work of Stefan Hermann (@CNCKitchen).
The originally generated GCode did not work on the K1 / K1 Max, so I specially modified it, to be printable on the K1 / K1 Max.
Download the GCode and print it. Then follow the great instructions on Stefan's website to evaluate it (https://www.cnckitchen.com/blog/extrusion-system-benchmark-tool-for-fast-prints.