The heat would probably be the same as any muffler next to a gas tank. its not right next to the manifolds, so it would cool down lots before entry into the turbo.
On that v8, he has torque to overcome the turbo lag. By the time the turbo kicks in, hes already hauling ass, and then you better hold on! Also, thats a lot of pressure going through the exhaust. It might not have as much lag as yall think since he is running a single exhaust to the turbo and after the turbo, letting the pressure build up fast.
Overall, thats a wise idea, he gets very cool air because its in the rear of the exhaust where everything is cooler than next to the block.
Kudos to that guy, thats a great design. Im just concerned about the filter placement, and the exposure the oil supply line has.