Hahahahaha.
If he sits in it maybe. Doubt it though, Had the Y pipe of my mates Calais for a couple of days and I had it running to let it warm up while I sat and watched the temp gauge. Got a tad smelly but not that horrible.
How the #### do you drive a car? Sitting on the roof? :hmmm:
For a week as well, Carbon Monoxide poisoning isn't something that just happens after 5 mins of exposure. It builds up in your system, a week is more than enough time for it to build up in your system to dangerous levels.
All it would take is one grommet in the floorpan to be slightly damaged or mis-aligned, or even the boot vents - in behind the rear bumper, the rear bar would act like a big funnel, sucking in the exhaust gasses constantly for the drive to work/shops/drug dealers house...
O/P, mate, exhausts are there for a reason, not just to make the exhaust quiet, but also to take the toxic gasses to a point where they can be vented to a safe place - ie, not the cabin of the vehicle.
done and done lol