I started using a piece of cardboard between my battery and the intake a few years ago, and it seemed to gave me about a 2 miles per gallon increase. (Though after building this, I received criticism that this will not help with gas mileage, but will help with performance!)
Now it was time for me to relocate my battery so now I have to make a Hot air block from scratch. I made this one from metal, and I expect better performance than my cardboard version.
This is the finished hot air block and my new battery box
I was using the stock battery mount location, with a normal tie down, but it kept having issues and getting loose. So then bought a replacement tie down, but that also came loose. I wanted to relocate the battery to the trunk, but I have way too many wires added in over time (inverter, fuel pump, 2x amps, and more). So I decided to relocate to about the same area under the hood, but lower and out of the way.
I have a 1988 Honda CRX. This car was built with a weaker pedal assembly then the newer models. Its a common problem for the clutch pedal to snap and bend. The later models are stronger and this should not happen.