Quote Originally Posted by Chebosto
Rear Diffuser Installation.

Level of Difficulty: Easy.
Time Needed: Approximately 30-45 minutes.

NOTE: Installation of the rear diffuser will cover the OEM rear tow hook location.

Tools needed: 10mm Deep socket & ratchet, 10mm open wrench (small, long handle if possible), masking tape, marking pen (sharpie), drill & assorted drill bits, and a friend (if you don’t have any friends, you may pay someone for an hour. The install should only take 30 minutes, but you can play Guitar Hero with your hired friend for the remaining time)

Optional Tools: Floor jack, jack stands, chocks or wooden block, loctite/thread lock

1. If you have factory rear mud flaps, or aftermarket rear skirts, please go ahead and REMOVE them from the car. Due to the design of this diffuser, you will be unable to use them and may interfere with proper mounting and placement of the diffuser to the underside of the car.

2. OPTIONAL: Chock the front wheels, and jack up the rear end of the car safely, and place the car on jack stands. Ensure the car is STABLE before getting underneath the car. This will give you ample room to drill holes to the bumper and reaching the final mounting points.

3. Start off by assembling the rear diffuser. The “elongated” Z shaped brackets, the one with two holes on the short side, and three holes on top, are to be mounted to the diffuser. These are used to attach the diffuser to the bottom sides of the OEM bumper.

4. Attach the side Vortex Generators. Smooth part should face down.

5. Using the picture below as a reference guide

6. Attach the rear mounting piece. This elongated U bracket attaches the rear diffuser to the back of the OEM bumper. If you feel that this direction would be difficult to tighten the bolts to the car, you may wish to flip this bracket around, so you can tighten the bolts from the top.

7. Using a friend, hold the diffuser up to the rear of the car, or prop it up using a box, or dead cat. Using the rear of the car as the reference point, the rear lip of the diffuser channel should come up to the natural crease line in the OEM bumper. Shown below.

8. Using the masking tape, tape the undersides of the OEM bumper on the sides and back center area where the mounting brackets should go, and using the sharpie make the necessary markings on the tape for where the bolts are to go. The diffuser should be ‘level’ and not skewed to one side or another. Re-adjust the bolts to the “Z” & “U” mounting brackets on the diffuser if the diffuser is not straight. See below.

9. The LEADING edge of the diffuser should line up with where the arc of the rear fender ends. See below.

10. After marking the correct mounting spots (three holes on each side, and two for the back of the bumper), No need to make the underside of the car look like swiss cheese, MEASURE TWICE. DRILL ONCE. Do it. Grow a pair. It’ll be ok. If you mess up with the alignment, there is enough play to make the diffuser look level. However, if you over-drilled the holes in your bumper, now is a good time to go out to get some extra washers to secure the diffuser properly. NEWB.

11. If the Diffuser does not clear your installed exhaust, certain modifications may be necessary. Drill, dremel, or cut at your own discretion. If you need to CUT into the leading edge flap on the diffuser, this will weaken the overall structure of the piece. Be sure to reinforce it with extra fiberglass and resin to stiffen it up.

12. After making the holes, remove the “Z” and “U” mounting brackets from the diffuser and using the appropriate mounting hardware included in the kit, and bolt the brackets to the bumper.

13. Attach the diffuser to the mounting brackets. The hardest part is getting your fingers in between the diffuser and the OEM bumper. Having a long & thin open wrench might help here.

14. Next, there are these two weird twisty metal brackets. These are mounting to the leading edge flap of the diffuser to the underside of the car. They will keep the front of the diffuser from dipping or falling. It is VERY important that these be mounted securely to the car. These brackets use pre-existing bolts on the chassis, finding them is sort of like a bad jig-saw puzzle. That’s in 3D. And in the dark. But it’s ok. These pictures should help you.

Driver side mount is behind the rear wheel along the fender liner.

Passenger side mount is up above near where the rear sub frame is attached.

15. After the leading edge brackets have been installed, re-check all the mounting bolts, they should be slightly tighter than hand torque specs. You want to have it secure, but not so much that you risk cracking the diffuser. If you want, you can use thread lock/loctite here.

16. Stand back and enjoy your newly installed diffuser.

17. Done.