Elbow tube going into throttle body.
 

Problem: OBD-2 Codes P0171/P0174 combined, Service Engine Light.

Found: Elbow tube going into the throttle body assembly, found the small tube almost completely sheared off.

Solution: Remove and replace Elbow tube, less than $20 for a new one.

Before I R/R the elbow tube, what other components of the fuel injection system should I inspect, replace or clean? I'm afraid that there may be a lot of dust build-up and may get the same codes even after replacing the elbow tube.

Replace the rubber boot/elbow and see if you get the same codes (Probably Not). No use speculating until you start repairing the obvious repairs.