The A/C slugging was too much oil at once and could damage the compressor. The revised plumbing got rid of a 'low spot' where refrigerant oil could pool and when the compressor engaged, it would take a gulp.
Since liquids don't compress very well, this sometimes took out a compressor.
If the system is low on oil, it could also be bad.
The IAC valve pintle and seat can be cleaned with solvent, toothbrush and rag. The throttle bore and blade also need to be cleaned of carbon where the air passes to prevent an air restriction. This is essentially a dealer's throttle body service.
The PCM will usually adjust the IAC more open to compensate for restricted air intake to maintain the correct idle speed.
Idle speed is an adaptive value. By disconnecting and reconnecting the battery, it will reset the PCM and idle speed will be relearned. Leave the vehicle to idle without giving it gas for a couple of minutes before driving it.