I don't know how much heat will be put into the air through a warm air supply tube like yours but wrapping it with insulation would help.
When I had a 1992 4/4 with 1.6 CVH engine my air supply was similar to yours and was melting underneath so was replaced and insulated.
Zircotec coating the manifold will cost you £250+ based on quotes for 4 cylinders.
Try exhaust wrap?
Air dam underneath the car to draw air out?
My current car - 2002 Plus8 - has a polished stainless filter housing and that gets to 40 degrees celcius after a short run with engine at normal temp!
