hi guys my car threw the service engine light on and after getting it scaned it gave me these codes p0156 and p0161 now i know both of these are from a 02 sensor i just don't know which one and i just recently changed my exhaust manifold on the drivers side so could this trigger the cel and my car seems to be tapping real loud from the middle of the engine are these related or different problems thanks in advance for the help.

 

I'm not sure on the o2 sensors. If you want to check for exhaust leaks get some hose and check manifold to exhaust. It really amplifies the sound. I used 3/4 inch heater hose I had.