Check the easy things first : Check all vacuum hoses an steel lines for leaks ,splits ,rotten or lose fittings . Check for missing vacuum caps on intake manifold on some models.
Check pvc valve and hose.
Check throttle bolts for tightness(3)
check air idle valve for looseness , there is a paper thin mounting gasket also check for rips. Same with the throttle position solenoid
check the air intake supply from map sensor to the throttle body for the same.
Another thought check the exhaust manifold for cracks.
Its a start