i tried looking for a thread about this, but gave up.
My CF hood and trunk are embarassing to look at. The clear coat is yellowing and looks terrible… suggestions? How do i bring it back to life? or is there a cheap way to give it a different look. My 07 WRX is black, i was considering plasti dipping the hood/trunk black… but i think it will look blah.
Painting it is pretty much your only viable option. Most of these aftermarket crap carbon companies use very cheap epoxy resin and/or gelcoat that is not UV stabilized. The yellowing you see is the gel or epoxy aging due to sunlight. If it has JUST started to tinge you can sometimes(VERY CAREFULLY) wet sand the gel coat and reduce the tinge, then immediately paint it with 3-4 coats of a high quality UV stabilized automotive clear and it can prevent further degradation.
Just one of many reasons why good carbon products are so much more expensive, because the proper components are substantially more expensive than poor quality general purpose resins. The cheapest resin I use here is WS105-207 which is an all weather epoxy, about $160 per gallon, and I use that for parts that may see weather/rain/sunlight for 50% of it’s life…
From my limited knowledge of reading things on here, plasti dip will most likely look out of place. Painting it would correct it but painting a trunk and hood correctly with blending to get the paint to match properly may end up costing you more than a new hood and trunk all together. Especially if you can find a good quality used cf hood/trunk in good shape. Posting pics may give the more experienced body guys on here a better idea of what you’re working with as well.
Adam said it. UV rays killed the epoxy. I have restored a few in the past by sanding it out (have to hope the yellowing is only surface deep or there about) and reclearing with autobody clear. 600 grit is what we use to prep already painted surfaces for another application on top… 600 on a DA will take quite a bit of material off quickly. I would sand a section, spray it with water and see if it is still yellow… water will simulate what the clear would make it look like once painted. If its still yellow, sand more, but you can only go sofar naturally and you don’t want to get into the weave.
Tinting the clear can cover up a little yellowing if its still there and you cant get it all out or you run out of epoxy to sand off.
We need to see it to see how bad it is… worst comes to worst like Eric said, color match it.
I wouldn’t even put a DA to it. Hand wet sand only. Most aftermarket carbon has super thin gelcoat(if there even is gelcoat, AKA the “dry carbon”) and if you go through well then you’ve just created a bigger repair problem. I can repair that type of damage but it’s something you want to avoid for sure.
If you want to wet sand this out, wrap some 600 around a flat paint stick(Lowes, HD) and wet sand it by hand carefully on a larger panel area. The paint stick will conform to the hood shape
If the UV damage is through the gel and into the epoxy then there’s no amount of sanding that will correct the problem, aside from sanding for paint prep 
You can usually tell if the hood ha gel on it by a finger nail test. Gelcoat is relatively soft and and area on the underside of the hood(not affected by the sunlight) will retain the original properties. If you can leave a mark in the gelcoat by pressing your fingernail into it hard(can use a wood paintstick as well) then there’s gel, if not then no gel and all aformentioned work to wet sand the damage away is moot. At that point it’s paint or replace.