No 100% sure... F1 cars are made out of carbon fibre, but the exhaust is usually wrapped in titanium. The engine must get hot, not what temperatures though. You'd need to ask someone far smarter than me :)

Motorcycle exhaust mufflers are commonly made of carbon fibre but it really depends on what you're putting this on and how far down stream from the exhaust it is. I've seen a lot of heat barriers made from carbon on cars and motorcycles. Also hoods are often replaced for carbon in racing and a lot of people have exhaust manifolds directly below them. What usually happens is the carbon gets discolored from the heat but not much worse unless it's directly touching, but that's another can of worms.