You need to de-bulk the carbon in the mould. If it is only 2 or 3 layers thick you can lay up the whole part and bag it. But you need to allow it to be pulled down in a full vacuum for  at least a couple of hours or longer.. I leave it over night with a full vacuum. 

I use a none perf with a breather cloth over the top only... No mesh and no peel ply apart from on the flange ONLY. I put breather cloth over the release film then over the whole mould back too.. 

We are about 200 feet above sea level.. Nothing in the greatest scheme of things... I dont have pinholes over my parts unless I have made a mistake when I lay up ... 

Adding UV stabilisation alters the chemistry of the resin and none of the epoxy resins used in pre-preg as far as I know are UV stable. Some are better than others but ALL of them yellow over time. A 2k lacquer is the best thing to get a good gloss...

Here is mine with a quick coat of lacquer from a cheap rattle can and not even a good 2k lacquer..



If you have pin holes at all you have not perfected using the material... It will have to be sprayed to get the best surface gloss that is UV stable.. But you can get a very VERY good gloss surface in a good mould if you wanted too... But cannot say how long it would take to discolour... it could be months or years... but it will not be UV stable..