Yes, they make a clear powder coating. Looks great too, but I never used it on an intake though. It can take temperatures up to 400 degrees, but over that it will probably yellow too.
Where'd you hear that clear powder coating will only withstand up to 400 degrees? And what kind of tune up do you have that your intake gets even hotter???
:wack:
Commercial spray / rattle can clears yellow over time. Clear powder coating will only yellow if it's applied incorrectly, or cured for too long or at too high of a temperature. It won't happen over time either -- it will happen immediately.
A brand new intake can be powder coated in clear and will last a very long time without any adverse effects. But I can't really in good conscience recommend only clearing a used intake -- unless it's completely outgassed, bead blasted and all the old fuel and impurities trapped in the metal are removed, it will have an uneven, splotchy looking finish ... and no one wants to preserve THAT.
I don't offer "advice" to people who are looking to put a turbo or an EFI setup on their Slant 6. If you really don't know the answer to a forum question just keep the opinions as your own. Bad information on ANY subject does no one any good and merely fosters the rumor mill.