Bringing down cabin air intake tempetures.
 

So on my last tank I got 38.47 MPG, now due to the current heat wave it is hard to advoid AC since on the uphill drive home my engine heats up my uninsulated hood to the point that the air going over the hood into the cabin air intake often is over 90F. I'd open the windows but I don't need the parachute like drag. How much insulation would I be able to get with in sunny socal, and what would make the best insulation material? I have to climb 700-800 feet in about 3 miles.

Your out in ventura? Probably not much. I wouldn't risk blowing up your motor if I was you... My advice, crack windows 25%, it's what I do, and tbh I notice a very, very small difference in MPG.

I need to get my OBDI to serial cable working. I know the car won't die going up the 14 from the 5 into palmdale on a 100 degree day, with AC on, with upper grill block, doing 70-75 MPH, without pinging (no knock sensor,) but that is the edge of what the cooling system can handle.

I have 1" foam (rubber) pipe insulation on the training edge of my hood as a wiper deflector, It also reduces a bit of glare off the hood. I used some velcro to flatten each end. Don't know if it helps with Aero or not, but I like to think so. I have also noticed it seems to have reduced the noise level a bit. Maybe cooler cabin air intake as well, lol...Cheap to try

Go to any junkyard or self-pull location, and get the under-hood insulation of another vehicle. I know it comes on most trucks, which would be plenty large enough to trim down to fit on your hood. Then you just need to mount it up.

Also, consider removing part of your grill block until the heat wave is over. No need to risk cooking anything.