The high heat inside the engine compartment can approach 200 degrees.
Most of the heat comes from the exhaust manifolds. I measure their temperature at 600 F and in the hot summer will get up to 700 F.
It doesn't take long to heat up the plastic and since it'* temp limit is about 200 F can be prone to melting. It has got to be transferring some heat into the intake charge.
You would be wise to leave the insulation on. No-one will know it is there except you and your mechanic.....probably the same person.
.....oh and maybe that Rustang you leave in your dust.