Ignore it (based on everyone's experience) the gauge is worthless; change the filter (Toyota or Ford); use thicker oil; or sell the vehicle before you go broke!
Didn;t read the whole thread so if this was already mentioned then ignore: etch your VIN on both cats and then paint in fluorescent orange or green. Any thief who sells to a legit buyer won't cut your's out.
Everybody used to have a rubber gasket under each cap, you now have hard plastic and leaks.
The PS cap really does leak when you drive and turn the wheel. Lil' bit at a time; over time.
Buy new caps or rubber gaskets. Done (for now).
Etch your VIN in each cat and paint them orange. Make the VIN visible to a thief. No recycler will them them. If they can't be bought, they won't be stolen.
There's a recent thread about using Pioneers in the rear. Clip and bend the tabs to fit. Use a tiny machine screw to secure. Just did mine. Search for "pioneer"