M3 LIP SPOILER
For this modification I Followed the directions given in the Audiworld tech section with the following difference.
It became apparent that it would take quite some time for the spoiler to become properly heated using a hair dryer so that I could bend it the necessary amount to fit on the S4 trunk lid.
So as an alternative to a heat gun/hair dryer I placed the spoiler between the cars windscreen and sunshade, with the car facing the sun. It was left there several hours during late morning and early afternoon for maximum heating.
Then I brought the spoiler inside and placed it on the counter and clamped it into the desired shape for it to cool. This was then repeated the following day.
After doing this twice the spoiler was close to being the desired curvature and was fairly easy to affix to the trunk lid.
This process of heating the spoiler took a little while to do, but involved minimal participation on my part, heated the spoiler evenly and thoroughly and made it quite warm.
I had the lip spoiler painted by a Ford dealership as they were the only place in town that carried the correct paint to match my Santorin car.
The M3 lip spoiler is holding up well as of July 2012 and I still like the change in look that it brings to the car.