Prusa i3 Prints Wrong Size

So i have a recently built prusa i3 rework and ive noticed the problem that for everything i print it 4/5 the size its should be on the x and y plane so to cope i've been scaling all prints by 1.25 in the x and y plane but now im trying some larger prints that cura thinks are gonna be too big for my bed but i know because of the scaling issue they will is there any way to either fix the scaling issue or override cura to prints anyways?

You need to fix the steps for your X and Y axis in Marlin, look for this line:

#define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,4000,530}

80 is for a 20 tooth pulley, if yours is different use the Prusa calculator:
[prusaprinters.org]

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My updated Instructable on our Prusa i3 Build
[www.instructables.com]

i have modify Prusa i3 x axis with lead screw. I want to set the DEFAULT_AXIS_STEPS_PER_UNIT of 4 digit on x axis. but the marlin only allows 3 digit number for x and y axis and only 4 digit for z axis. so please help me to modify the marlin

so i have 16 teeth pulley so i used the calculator and it told me to change them to 100 steps but now its not printing in the center of the bed and it seems like there are gaps between the infill