This mod improves exhaust and noise. All components can be printed with X Plus3. No modification of the printer body is required, but the spool case can no longer be fixed to the back of the printer. All materials are PLA; PETG may be preferable for the "core" parts. 0.2mm strength profile of QIDI slicer is used as a base and the bottom solid layer is increased to 5. This may be overkill.

The exhaust hose fits 100mm (4inch) diameter.
25mm thick fan is assumed. If using a 12V fan for the PC, a 24V to 12V DCDC converter is required.
Back panel will be printed upside down for better appearance.
The fan box and upper panel will require additional support at printing.
Additional screws and the same number of nuts as below are required. You might want to put washers between them as well.

When using an 80mm or 120mm fan:
M3x10mm : 7
Fan screws (taper screws) :8(for front and back) or M4x40mm : 4

If using 40mm fan:
M3x10mm : 7
M3x15mm : 4

Attention

There appear to be variations of the X-Plus3 with different chamber fan and carbon filter box mounting configurations depending on when they were purchased. Currently, this kit is only compatible with the type shown in the picture. 80mm chamber fan, square cutoff and carbon filter box secured with tapping screws.

Assembly

Turn off the printer and remove the back panel. Do not lose any screws, as you will need all of them. Unplug the fan connector from the board.

Insert the M3 nuts on the back side of the "core" part. Remove the screws holding the chamber fan and carbon filter box in place and separate the cable ties that hold the cables from the stepper motor. Then fasten the "core" part to the carbon filter box. Fan cables should be routed through the grooves on the back side.

Clean the surface of the fan box where the support was attached as much as possible before installing the fan.
For 40 mm fans, fasten the fan to the adapter plate with M3x15 mm screws.

Fasten the connector and fan box to the back panel using M3x10mm screws. The connector is inside and the fan box is outside. Use two "assembly helper clip" to hold the back panel in place for easier assembly. For 40 mm fans, use an adapter plate instead of the box.
Due to the large opening, it is recommended to install fan guards on both the inside and outside to prevent cables and other objects from getting caught in the box. I prefer metal ones, but you can also 3D print them.

Use the original tapping screws to secure the upper panel and the connected back panel to the printer body. Note that the screw holes used have been moved. The additional hole in the upper center of the back panel is connected to the "core" part with an M3x10mm screw.

To connect an exhaust hose, connect the hose to the adapter and fix it to the threaded part of the core.

NOTE

Attention to the positive-negative of the fan connector terminal. This is opposite to cables with XH connectors on the market. I have flipped the connection as shown in the picture.