Installed the carbon fiber front splitter yesterday on my M3. I used the 3M tape method, based on this Eurotuner youtube video:
The video made it look fast and easy, but it took me about 1.5 hours! But then again, I was taking iPhone pictures along the way. Here's the steps I took for the driver's side:
Pic 1) Got hex screws (07147129160), clips (07146951655), and install instructions from BMW. There is one existing screw/clip on front bumper, so that can be re-used. The hex screw ($2.49) and clip ($1.85) for center hole are new and the last remaining hole was not used.
Pic 2) Clear bra top part of splitter to protect from rock chips and scrapes. Went to Ross to pick up iPad 2-pack screen protectors ($7.99) and applied to bottom part of splitter (where it can't be seen).
Pic 3) Jacked up one side of car and unscrewed three screws at bottom of front bumper. Then dry fit splitter onto the bumper and drilled new hole into bumper. Unscrewed three more screws in front wheel well to remove the plastic tray.
Pic 4) Made notch in the plastic tray, so clip can fit over the newly drilled hole.
Pic 5) Installed the metal clip.
Pic 6) Installed plastic tray (with new metal clip) back onto car. Put back all the screws, except for the two holes that hold the splitter.
Pic 7) Got 3M tape ($9.99) from auto parts store.
Pic 8) Placed 3M tape onto splitter. The video only placed tape on the top, but I placed at three locations (for added grip and where you won't notice thickness of tape).
Pic 9) Installed splitter onto car, screwed in the two bottom screws and removed red liner of tape (while pressing splitter firmly onto the bumper).
Pic 10) Done!
Of course, this was all overkill since the splitters do not weigh anything! You really do not need to install that extra metal clip. If you want to save time, just drill new hole into bumper and screw hex into the plastic tray (because the tray is strong enough to hold the splitter without metal clip). Good luck!