16555/P0171/000369 - Fuel Trim; Bank 1: System Too Lean
Possible Causes
Mass Air Flow Sensor (G70) defective
Intake System Leak(s)
Possible Solutions
Check Mass Air Flow Sensor (G70)
Check Fuel Pressure Regulation
Check Fuel Pump
Check Injectors
Check Intake System for Leaks
Check Exhaust System for Leaks
Check Secondary Air System for Leaks
Check Vacuum Pipes for Leaks
16795/P0411/001041 - Secondary Air Injection System: Incorrect Flow Detected
Possible Symptoms
Malfunction Indicator Light (MIL) ON
Possible Causes
Fuel Pump Relay (J17) faulty
Hoses/Pipes to/between Components faulty/clogged
Secondary Air Injection Pump (V101) faulty
Secondary Air Injection Pump Relay (J299) faulty
Secondary Air Injection Solenoid Valve (N112) faulty
Possible Solutions
Check Fuel Pump Relay (J17)
Check Hoses/Pipes to/between Components
Check Secondary Air Injection Hoses/Pipes for Carbonization
Check Secondary Air Injection Pump (V101)
Check Secondary Air Injection Pump Relay (J299)
Check Secondary Air Injection Solenoid Valve (N112)
(rosstech wiki)
This happened to my car when I first got it too. I had an exhaust leak, it might of had to do with the flex pipe, I cant remember. But if its getting loud, you most definitely have an exhaust leak. That could be causing other problems too. Your MAF might be dirty as well. You also could have a vaccuum leak.
I would start off by inspecting your exhaust. Also, pick up a can of MAF cleaner (there is a DIY on this sight on how to clean you Mass Air Flow sensor) and clean the MAF. Visual inspection of the exhaust and intake system would help. You might be able to hear a vaccuum leak. But definitely start with the exhaust.