A nice quick check of your cat converters function.
comparing both sensor voltages,a good pre mot check to ensure emissions pass
Engine valves can have some very subtle and difficult t o diagnose issues.
Loose valve seats will cause some real headaches.The only method for seeing these issues in real time is via the in cylinder waveform.
The conventional compression test is useless in revealing these issues
There are many non invasive techniques for testing your engines components.
Checking the fuel pumps current pull using an amp clamp and an oscilloscope is a well known one.
Rather than rummage under the car and start taking up seats etc,finding the fuel pump relay and bridging the power pins then clamping the cable is way easier.