^ i took my lid off and its haning on my garage wall. Taking the hood off decreases the temps and introduces better airflow. Its there for only show anyway. I think in the future you could hollow out a portion of the hood underneath and than cut out the duct out of the cowl....That whole portion is completely hollow so its an aftermarket hood practically ready to get cut
I would love to see the data on this. If you put a microphone near the driver's headrest, what kind of db or frequency change could there possibly be over all rpm and load conditions? At least it shows that GM still has a development budget for the LSA which is good.
Mine was an 04/09 build and has the plate. I tapped on the plate and it seems substantial enough that it won't bend with the pressure increase you might get with an overboost. Seems more like an access cover for something. Maybe it is for a forced induction hood inlet, although its location under the brace is awkward. Possible that it is a production cover that is from some other application and is cheaper for GM to buy with the plate, instead of the ribs. I would go with the last answer as most likely. Occams Razor and all that.