Rear diffuser
The stock rear bumper has a grey plastic center panel with an exhaust cut-out. It adds width and dimension to the rear but is slightly bland. The replacement part from BMW Performance, however, is significantly more attractive, not least because it's manufactured to a very high standard in carbon fiber using technology developed for the M3 program. The new piece features more detail, mesh vents and it again fits in seconds. Thank goodness we also have the carbon trunk spoiler, because the material is such high quality you want to look at it again and again.
 Stock plastic part looks rather...  Stock plastic part looks rather bland compared to BMW Performance carbon diffuser |  There are six 8mm bolts under...  There are six 8mm bolts under the rear panel. Undo them to release the lower section |  Use a plastic wedge to release...  Use a plastic wedge to release the clips at the top of the panel |
 Pull the panel out of the...  Pull the panel out of the clips carefully so you don't break any |  Spray WD40 onto the clips...  Spray WD40 onto the clips and push the diffuser into place. Five screws go into the underside but don't overtighten or the carbon could break |  Now doesn't that look so much...  Now doesn't that look so much better than stock? |
Trunk spoiler
I must confess to being very fond of the stock trunk spoiler. It's subtle lip say "sporty" without shouting it too loud. However, the carbon replacement from BMW Performance oozes class with its perfect composite weave and sleek styling.
The new wing is bonded to the car and takes very little time to fit, provided you have a steady hand. Removing the old spoiler was remarkably easy and the rubber wheel to remove the bonding residue was a revelation. We'd never seen one in action before and it didn't leave a mark on the paintwork. If you don't have one of these, you'll need to patiently use adhesive remover.
 The BMW Performance rear diffuser...  The BMW Performance rear diffuser and trunk spoiler are some of the nice carbon fiber pieces we've seen |  To begin removing the stock...  To begin removing the stock spoiler, apply tape to both sides to protect the paintwork |  Then slide a metal spatula...  Then slide a metal spatula under the spoiler and run it the length of the part |
 Apply steady pressure and...  Apply steady pressure and the spatula slides under the spoiler like butter |  Once the stock part is removd,...  Once the stock part is removd, a residue of tape and glue remain on the trunk |  A rubber wheel on a drill...  A rubber wheel on a drill removes the tape and glue residue, leaving the paintwork unscratched |
 Tape the wing into the position...  Tape the wing into the position you want it and run tape along the edge so you have a guide to when you glue it down. Measure both sides to ensure it's centered |  After preparing the surface...  After preparing the surface with the supplied adhesive promoter, apply double-sided automotive tape along the leading edge |  Prepare the center contact...  Prepare the center contact surface and again apply tape |
 Without removing the backing...  Without removing the backing to the adhesive tape, fix the wing in position again with masking tape. Then lift one corner slightly and peel off the backing, pressing down as you go to make it stick. |  Do the same with the second...  Do the same with the second piece of automotive tape under the spoiler - peel and press down as you go |  Stuck firmly and looking superb;...  Stuck firmly and looking superb; our new carbon fiber rear wing attracts plenty of comments |