|by a reputable powdercoating outfit (owner races a tube frame 300ZX with L28) and is knowledgeable on thermal ceramic coatings.
Manifolds and turbine wheel sections done on mine and Mixman's cars. Track tested and inspected after years of use, coatings hold up fine and keep the heat in the exhaust sections.
Pricing was in the couple hundred range for a set of manis and turbine sections. I'd go shopping locally and see what's in your area.