<VV> Three of what are sure to be many turbo questions

[Norman Witte]

The muffler on the new turbo is toast.  At least some of the exhaust system is there, because it made some pressure when I drove the car.  However, when the motor comes out, I intend to replace the entire exhaust system.  Reading the Basics manual and Bob Helt's book I read about using Jet Hot coatings on turbo exhaust plumbing.  

1.  Which pipes should be coated?  Crossover, inlet and outlet pipe?  Exhaust manifolds?
2.  Anyone have any experience on the costs of doing this?
3.  I was reading in Bob's book about performance gains from using the 180 impeller with the 150 exhaust turbine.  What's involved in making this mod, and what kind of experiences have people had with it?  (Okay, I know that that is two questions.)

TIA

Norm Witte