To uncover my opinion a bit, I've designed quite a bit of stuff in my career including covers and plastic (some refer to them loosely as composite because of the added glass fibre in the resin) intake manifolds, from 2 piece clamshell injected molded (and for Chrysler in the past) to lost core technology. Plastic manifolds are lighter and cheaper to manufacture depending on the volume, but aluminum can be feasible, in the end it comes down to consolidating features (injector bores, etc.), smooth runners, mold tooling, material costs and post machining. It's always been a goal of mine to design functional and good looking parts and always thought it was cool that Vipers didn't have large engine covers like the masses. Engine covers typically are used to isolate engine noises, and sometimes for Ped-Pro (pedestrian protection, when a person slams onto a hood it can shield sharp engine objects from piercing the hood or absorb some of the impact energy), as well as an attempt to clean up the look hiding electrical components, injectors, etc.. as what they typically refer to this as being perceived quality.
You are correct that you can never please everyone, been dealing with that my entire career in automotive design in many aspects, yet we should all feel free to share an opinion.
Here's a couple more engine pics without large plastic covers, first one definitely costs less than a Ferrari or Lamborghini, only reason that I showed those pics previously were because of the Italian influence in the previous Viper engine design appearance being aluminum / magnesium with crinkle paint / rough surfaces and bright machined highlights, etc..
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Cheers,
Mike