If your MINI is suffering from Inconsistent Under Extrusion or Excessive Stringing after using it for Multiple Years, you may need to Replace the Bowden Tube
After a few years of using the prusa mini I found the print quality had degraded quite a bit from how it performed when it was new. I've tried everything from extruder cleaning, Hotend PTFE replacements, High Flow Nozzles, and Every kind of settings tweaks, eventually I thought maybe the bowden tube might be a bit worn out, so I got some fresh 1.9mm ID PTFE Tube, and followed the instructions on how to make a new tube with the included "olives" When I cut the old tube in half to get the nuts, I was shocked by just how much ware had occurred, It was almost breaking through the side lol.
After replacing the tube, the printer works almost good as new, with noticeably less stringing, less visible seams, and Perimeter walls that don't separate from each other.
Hope anyone else who's had this printer for a while with similar issues finds this helpful.