every little bit helps. just look at what speedjunky01 said. 16.4 to 16.8 in a night due to heatsink (i doubt he was becoming a worse and worse driver) thats kind of a big deal.Painting for appearance makes sense.... I've used bbq paint from home depot a few times.
But, how long does the air actually sit in the intake? a tenth of a second? .. I think it makes more sense to pay attention to intake location than worrying about heatsink