I'm looking for some general advice on making an intake plenum to suit a low boost turbo engine (7 PSI) out of carbon fiber using vacuum infusion, utilising my 3D printer to create the mould. This would be the first carbon fibre part that I've made, based on a design drawn up in Autodesk Fusion 360 shown below.

So far I've spent a few days doing research online, reading other posts in this forum relating to intake manifolds and 3D printing moulds and watched numerous videos on producing carbon fibre parts. However I still have a few open points I'd like to get peoples opinion on. 

• Based on the plenum shape I'm assuming I would create a positive mould.
• Should I use tooling gel or something like 3M Super 77 sparingly to ensure the CF attaches to the shape.  
  
• Does this sound right to create a 3D printed mould; use PLA filament, smooth down the edges, spray a few coats of plastic filler primer and seal with S120 mould sealer.
• For the 4 bolt end flange I'm guessing this can't really be formed using CF. Instead could I go about inserting an aluminium flange that could form part of the mould and be covered in CF. Would this hold up under boost? 
• Layer up wall thickness to be around 2mm, from what I've read this would be strong enough.

A positive mould would be something you would remove after the resin has cured. This is just the part printed as you want it to be in the final shape, am I right? There is no way you could remove the printed model out of the carbon piece, without destroying either. Plus, your measurements would be wrong in the end, because both flanges will be of by the thickness of the print.
A positive mould should look like the body that fills your 3d model. Without the flanges. To get your carbon part like your drawing, this body has to be placed on a flat board, that "forms" the big flange, and a small metal plate could be attached to the intake end of the body, to create a plane to form the small flange. After the resin is cured, you could remove the board and the metal plate, and if your geometry is right, you should be able to draw the 3d printed positive mould out of your crp part.
As I read your post again, I guess you are thinking about just covering the 3d printed part with carbon. I don't think this is a good idea, because of the temperatures inside the motor bay. especially with a turbo. This could cause countless problems.
In this case, primer and mould sealer would be unnecessary products.
In my opinion, you might think about a far easier and not structural part to start your composite experience. The way I see it, there is much to learn for you, before you could master such a slightly advanced piece.