My interest in composites for my Marcos project started as a way to create a part that was too expensive to CNC machine out of aluminium. The V8 engine originally lived in a 2001 Range Rover - plenty of room under the bonnet. The Marcos is a much smaller car with a very low bonnet line. This has required a rethink on the inlet manifold design. While I can keep the cast runners, I have had to discard the single large throttle body. I will use two 48mm Jenvey throttle bodies. To mount these new throttle bodies I will need two asymmetric mini-manifold parts. Here is a rendered view of the CAD model...

Just make your own pattern then.

Depending on how many you want either use your pattern to make the part or take moulds off it then cast parts from them

All this is variable on what you are going to make the finished item from ? will it see vac/temp/pressure etc

For a one off in a rush (in like the car had to leave the factory in 5 hrs !) had good results making a quick pattern in p38 !