You need to look for the front O2 voltage to drop when the air pump test is triggered and make sure it is dropping. ( The test runs after engine warm up and engine at idle ) Is there a way to trigger the system through a scan tool?

The 97 era cars have a vacuum solenoid and a vacuum operated valve that allows air to enter the exhaust stream. Make sure this system is working as well.

This might be the engine with air passages in the head that clog up.

For a different engine, I had pitched the possibility of intercepting the O2 signal and reducing it when the air pump is running as a way to fool the computer. You would need a relay wired to be triggered by air pump power. Gold relay contacts are preferred since we are dealing with low voltage / current as silver contacts don't age well in that application and will increase resistance over time.