If you're ever feeling a little dumb, take solace in the fact that at least you didn't cook up the masterpiece you see pictured above.
Unless of course you DID concoct this home-fabricated abomination, in which case you should probably just go ahead and book a vasectomy right now.
Here's why muffler-mounting your turbos is a shithouse idea: turbochargers work by converting the heat energy in exhaust gasses into mechanical energy, which in turn is used to spin an air compressor that feeds into the engine.
Put the turbo way down at the end of the exhaust plumbing and you've lost a tonne of exhaust heat and gas velocity, which makes the turbocharger much less efficient at boosting power. Shooting yourself in the foot, is the scientific term.
Besides, it looks completely stupid. Even more stupid than the rear-seat-mounted turbos below.