Here's picture of my 26R engine bay.
The TTR shell is a super lightweight version so very thin and also a very dry layup. You can just see a fine silver line on the inner top edge of the passenger footwell, this is the reflective heat material which is a stiff but malleable aluminium matrix material. The headers are thin wall stainless, no ceramic coating and no wrap as I don't like the stuff, this is the second last of 4 sets I had made, the first set is on an Elan that cover over 35,000miles in 9 years no cracks, the other on race engine, no cracks, and this set, its done dyno time, post rebuild set up time, practice at 2 meetings and a few races so far, no cracking so far. The extractors have bolted slip joints where the 4:2 and again at the 2:1 joint points and good support at gearbox.
The wiring is also contained in heat proof tubing for good measure. clutch mater cylinder is concentric so no heat issue to worry about.
Not sure of the stainless # used but will check, its commonly used on custom race systems that are made for Porsche's current crop of race cars and two stroke expansion chambers, both made by joining two flat panels that are then pumped up to form perfect radiused extractor tubes, I've watched them being drawn up prior to cutting from sheet and being seam welded and pumped up, its a complex piece of craftmanship.
BTW The chap that makes them has also built his own 12 cylinder quad cam 24 valve power boat race engine from scratch!
I've recently had my S2 7 headers and also the original inlet manifolds ceramic coated inside and out and that has made a significant difference to the temperatures of the carburettors. Like Rohan the finish does not mark Silver for headers and black for the manifolds so they remain looking like standard finish.
Cheers
Vaughan