* Air pump: This refers to a secondary air injection pump used for emissions control. It pumps air into the exhaust system to help burn off unspent fuel and reduce pollutants. It's part of the engine's emission system, not the suspension.
* Ride compressor (suspension compressor): This is a compressor that pumps air into the air springs (air bags) of the car's suspension system. This is what adjusts the ride height and provides the self-leveling function in vehicles with air suspension.
A 1987 Cadillac DeVille might have an air pump, but only higher-end models of that era (and later years) had air suspension requiring a ride compressor. If your DeVille has air suspension, it will definitely have a ride compressor. The two systems are entirely separate and serve different purposes.
