Interference between instruments

Linking a couple of recent threads: Connecting multiple varios and how to change ASI markings....

I discovered the reason for a flight computer's inconsistent readings was the bezel on the ASI not being tight enough to seal. Snugging it up resulted in a more accurate ASI and flight computer.
Checking each instrument is a good winter project. Techniques are described in the back of Reichmann's "Cross-Country Soaring".
Jim