Anything under the bonnet?

Big flashy wheels, zenon headlights and car spoilers are the typical signs of a boy-racer, but is there any real value in a spoiler?
There's no doubt some value in having decent wheels and tires along with effective headlights, but car spoilers do actually serve a purpose. At higher speeds, the spoiler generates down-thrust keeping the rear wheels firmly on the ground and adding a degree of stability to the vehicle. There is an argument that this can increase aerodynamics and fuel-efficiency, but you might be better off slowing down to a speed where you don't need a spoiler if saving the planet is your aim.
Making an impression is a meld of performance and attractiveness and we can apply that to all aspects of life. If you perform well and look good you're doing OK, if you perform well, but look drab you are doing yourself a dis-service. Worst of all is if you look great, but have 'nothing under the bonnet'....
This can be applied to how you perform at work, how your blog looks or whether your car suits your personality...