it's hot...
opening up the air filters assembly does help flow...but it just flows hot underhood air.it won't help much, imop...gotta feed it cooler air.getting it from the grill under the windshield is a good spot.ever drive your cucv in rain?notice that there is a portion of the hood where the water is actually pushed forwards away from the base of the windshield...it's a built in high pressure zone.there's a reason that Nascar racers have tapped the windshield base for an air supply for years.the faster you go,the more pressure you get.cold air AND a small amount of boost.(assuming your intake ducting is properly sealed).The cucv's tall,blunt windshield makes lots of pressure in that area.More pressure,i think,than the regular grill intake port.
i've thought of doing this myself,but can't get past the "cutting a hole" part.The regular intake point at the grill is already there,with a built in punch plate,just ready to be popped out...so why not use it? it's certainly worthy of an experiment though.i think the best spot would be in the firewall,right in the middle of the windshield,directly behind the air filter assembly and just above the glowplug resistor pack.some sort of intake grill would have to be devised to deal with bugs and leaves,as well as the excess rain water that flows in that drainage area at the windshield base before it gets to the filter.
mike-pop...the only real effective way to address issues at high altitude is a turbo.normally asperated 6.2's,with there meager redline, can only flow so much...thats just the way it is.the exaust mods would likely help your egt's a lot though.