[Phantom]

I do not see wrapping the pipe before the turbo to be worth the trouble unless you want to keep other things cooler. Hotter exhaust does move faster but it also heats the air entering the engine more and if to hot that can hurt the performance of the engine.

I would not consider a turbo a heat engine but more of a water wheel (air is a fluid). Hot exhaust moves faster than if it was cool but cooler exhaust is more dense allowing for it to have more force. The issue is where the crossover point is between the two. Going back to the water wheel idea think of it like this powering it with a 1/4" hose at 60psi or powering it with a 1/2" hose at 30psi you can get the same amount of work completed. If you can get more pressure or more water out of a setup between the two you will have a gain in performance. (For reference size of hose is in relation to density and psi is to speed.)

I do not have any clue how to calculate the change in density of the exhaust in relation to the change in speed of the gas and its ability to do work.

One thing I will recommend is to keep the exhaust temp up after the turbo so it does not slow causing back pressure.