I have updated part list, 3D model (MPD) and building instructions on http://rebrickable.com/mocs/MOC-8003/jb70/42056-pimp-up-my-porsche/.
Changes:
remove pin clutch as suggested by @Kumbbl, I used 2 yellow axles 7L and 9L instead, that looks better
Mount seats to body as suggested by @DayWalker, Cool idea, this makes it much easier to remove the body
adjust front calipers as suggested by @DayWalker, easy change, looks much better now
remove 2L axle pin as detected by @Paknaloid, this was an error in my building instructions. This part is not needed
Thankx for your help to improve this great model.