High idle speed on 1994 Cadillac Seville

My mechanic can't seem to fix the idle speed. He's put in plugs and wires. He's set it to specs. I mean he has all the code readers and tools and knowledge.
Could this be the O2 sensor?

Asked by for the 1994 Cadillac Seville
check all the sensors like the tps, iac and make sure it doesnt have a vaccuum leak