I would recommend gaskets on the inlet side to get cold air in, and an internally applied ceramic coating on the exhaust manifold to at least the second radius in the curvature, but the whole manifold if possible.
I've had excellent success with this for bikes and v8s in the last few years, but the ceramic work is expensive (and someone else was paying).
When I can find someone over here to do my manifold at a reasonable cost and give guarantees about longevity, especially where a catalytic convertor is concerned, I will have it done for my own car.
Back in the day we tested tubular manifolds with: outside coating, inside coating and gaskets.
The dyno results were all similar. The running results:
O.C worked well for gas velocity, which translated to high end power, but gave poor part load results due to heat build up and transfer back to the head, which affected pace lap pull aways and deep hairpins.
I.C also did well as above, but the throttle response on hot, slow pull away was much better.
Gaskets were almost the same as the O.C, but with more throttle lag reported on the hot pull away.
The fairings gave good airflow and so the component cooling aspect was shown to be important. The mixed convection and low-grade radiation from the pipes themselves added to response, which only could be had with I.C.
I should, however, point out we were arguing over 1.25bhp at around 13500rpm on 150bhp 750cc engines traveling at 45-145mph, and throttle transients in the small fractions of seconds.
I've spoken with others who tried similar and the majority, but not all, found the same.
It's highly dependent on the installation - engine position, aerodynamic set up and, exhaust system length (do we need the heat further down?) from what my discussions and own work have generated.
Hence, with a bigger, more enclosed, thicker steel-walled exhaust pipe and a bigger head that sees very little air cooling, and, of course, a lot more thermal mass, I make the previous recommendation.
The very best recommendation I can make for engine bays in cars is that the actual exhaust material is a huge driving factor. I would choose a material that has a low specific heat capacity but a high meting point and low tendency to harden or fatigue with thermal cycling and vibration. Iconel and titanium are good choices, although looking to the future you are about to see some spectacular exhausts at the high-end of competition with metal matrix composite sections rather than pure metals.
Not a great answer, but hopefully there is food for thought.