Here are some noteworthy parts in current use.

Part Part Number Image Recent Source
Negative ion generator unit, single output.
Negative ion generator unit, quad output.
Drok DC voltage converter/regulator, wide range of input, 12 VDC output.
Note the hardened waterproof packaging, rather nice for the engine environment. Drok and other makes also have similar units with screw-adjustable voltage output.
Fuse tap for any size fuse.
Many on the market are rated at 10A max, which limits which OEM fuse socket you can safely use. This one and a few others out there, will let you use any socket up to 20A. Many vehicles use different form-factors for engine compartment fuses; be sure you get yours.
Car Add-A-Circuit
3M Dual Lock fastening material.
I laid a small bed of this in the air filter compartment, then cut sections to size to hold each item. Install only when air temperature is above 65F/18C; holds very well in all temperatures after install.
These things are great. They keep wires very securely connected, protected enough, and nicely removable too. They come in lots of shapes and sizes. This is the shape I’m using so far. The link is to a three-conductor version. One can buy an assortment at astonishingly low prices from many vendors. Fill the holes with dielectric grease for waterproofing.
Temperature-controlled switch.
This is an excellent component of standard part number, made by quite a few different manufacturers in different locations, and lately (March 2024) the prices have been going down, not up.
RPM switch.
I tried two sub-$100 RPM switches, but both of them malfunctioned on the Tahoe. This one is working very well. I am using it with the MSD 8677 adjustable low-RPM module, because it needs to be set to turn on just off idle.
MSD 8950