This is a design for a generic automotive part, which allows you to print as 3 separate pieces that fit on a standard size printer bed. It's a remix of a design originally by TinaBelcher, thanks Tina!

Designed to fit my 2017 Focus ST LZ, but should fit the 2013-2018 years I would think.

The joining tabs will take a M5 or 10-32 bolts/screws/nuts/washers. I also used a bead of sikaflex between the pieces and cleaned off what squeezed out when assembling mine.

To attach the assembly to the car, I used ¼-28 bolts/washer/nuts, but you could also use M6 hardware.

As this sits at the front of a car I'd recommend printing from ABS, PETG or something sturdy.

Settings that worked for me in PrusaSlicer printing ABS on a Prusa i3 Mk2 inside an enclosure that was preheated for an hour before printing, with a layer of gluestick on the (heated) bed:

'Flare' Part:
-Orientation as imported.
-0.15 OPTIMAL
-Infill 50%
-10mm Brim
-No supports.

'Inlet' and 'Outlet' Parts:
-Orientation: Using 'Place on Face' on highest flat edge when imported.
-0.15 OPTIMAL
----------Layers and Perimeters----------
-Vertical shell perimeters: 3
----------Infill----------
-Fill Density: 50%
-Fill Pattern: Gyroid
----------Skirt and Brim----------
-10mm Brim
----------Support Material----------
-Generate support material: Yes
-Auto generated supports: Yes
-Overhang threshold: 0
-Contact Z distance: 0.2 (detachable)
-Pattern: Honeycomb
-Support on build plate only: Yes

Included are my solidwork part files, try not to judge too hard as I've only learned through trial and error :)