Question for those in ITA running a 16V, or anyone else who can offer feedback. Legal and beneficial to coat the outside of the intake manifold?

GCR 9.1.3.D.1.q
The application and/or use of any painting, coating, plating, or impregnating substance (i.e. anti-friction, thermal barrier....) to any internal engine surface, including intake manifold internal surface, is prohibited.
So does this mean it's legal to coat the outside of the intake manifold? Reason I'm asking is because I've noticed that my 1.8L 16V intake manifold gets awfully hot, and that can't be good for intake air temps. Would coating the outside with the recommended Swaintech coating be beneficial for reducing intake air temps?
https://improvedtouring.com...hlight=thermal

For the same reason I was thinking of getting my header coated, and it's quite clear that is legal.
GCR 9.1.3.D.1.g
Any exhaust header and exhaust system may be used....