Silver intakes... hmm, might have to investigate.
The exhaust is a custom made one by a mate of the guy who owned the car before me, but KTec do a similar one for the 172. Basically, the backbox itself is in the same position as OEM, and a pipe just goes across the bumper, feeding the two 'mock' pipes you see out the back. So the spare wheel isn't affected.
I'm considering selling the backbox / bumper combo if anyone's interested...