Better guided filament path, using a closely fitted piece of PTFE tube.
Added channel for filament shavings to exit the extruder, avoiding the spur gears.
Increased clearance for manually cleaning the drive gear profile.
- -OPTIONAL- ~25mm (Dremel bit) cleaning wheel, inspired by the Flexion extruder.
- -OR- smoother inspection door operation.
Increased contact area handling accidentally moving/parking the Z-axis out of bounds.

Note: The cleaning wheel is an experimental and optional addition.
If you add one, I recommend ordering a spare feeder gear, in case your wheel damages it.
I am using a polishing wheel meant for soft metals and plastics (with sides printed in the very filament which my original extruder struggled with), which has not caused any extra wear yet.

Requirements

Almost all hardware can be re-used from the original extruder assembly, supplemented with the following spare parts (which were included with the printer):

4x2x25, preferably longer, PTFE tube (order another replacement if you use the spare, alternatively use your own or shorten the reverse bowden).
3 fresh zip ties.
-OPTIONAL- M3x8 bolt (for the cleaning wheel).

Print in PETG with the 0,2mm QUALITY profile, the spur gear protecting wall needs support and I recommend increasing fill density to 100% around the cleaning wheel mount.
Preferably use the supplied GCODE or PrusaSlicer project, these are fully pre-configured.
When using the PEI sheet, remember to add gluestick before printing.

Installation

Remove the original extruder, cut the zip ties and remove all fasteners and other hardware from the printed parts that will be replaced.
Do not disassemble the idler lever and leave the short piece of PTFE tube in the old piece (to prevent loosing it).
Using the modified printed parts instead, follow the Original Prusa MINI+which kit assembly v1.08, starting at step 34, up until step 41.
Use the feeder gear and idler lever to precisely carve the tip of the added PTFE tube to shape, with a small hobby or break-off knife.
Push the tube in from the threaded hole, pull it out again with the needle nose pliers that came with the printer, repeat this as often as you need to get the shape right.
Before continuing, make sure the carved profile matches the gear and bearing exactly, mind the filament gripping profile and correct position of the idler.
Measure the distance of the carved tube tip (or other measurable spot) to the flat side above the thread.
Cut the tube to stick out approximately half a millimetre more than this when pushed in the brass nut.
Use the feeder gear and idler lever to push the tube in the correct position.
Try to get this right the first time to prevent having to grab the freshly cut side with pliers.
Continue the Original Prusa MINI+ kit assembly v1.08 instructions at step 42, up until step 48 (as we did not prepare any Haribo Bears, sorry).
Bolt on the brass nut of the tube leading to the print head.
While I did not find it necessary, you may disconnect the tube first to prevent twisting it.
Finish the mod by step 14 up until step 15 of the next chapter of the Original Prusa MINI+ kit assembly v1.08.
-OPTIONAL- Remove the inspection door and its bolt fully, you can hold the door open to use the threads against the plastic.
Attach the assembly again with the M3x8 bolt, the bolt head should be slightly recessed in the inner hole when tightened.
Use the M3x30 you removed to form threads in the cleaning wheel mount, only bolting until it touches the Z-carriage, then remove it again.
Now attach your cleaning wheel, make sure it stays in place yet spins freely on the smooth section of the bolt while the printer is extruding.