ECU will not go into emission ready. Possible manifold crack?

[6GL]

Just as I received my registration and smog requirements my chenck engine light came on P0172. System too rich.

I cleaned off MAF sensor, checked for vacuum leaks, checked O2 sensors, ran 2 bottles of fuel system cleaner just in case. Cleared code. Drove for over 150 miles on a camping trip and light came back on when I reached destination. I cleared it again. Before heading home. Has not retured since over 200 miles now. Went to smog they said to keep driving as Catalytic monitor is still not ready. What is taking so long?

As i was looking under car searching for any issues with catalytic, did not find any.
What I did notice is a possible hairline crack in one of the exhaust manifold. See pictures. Can anyone help put their opinion if its indeed a crack?

MAF sensor 1 yr old
02 sensors 4 yrs old
Catalytic converter 8 yr old Magnuson direct fit.
Injectors 3-4 yrs old
Fuel pump 4 yrs old
Vacuum hoses have all been replaced over the years 4-8 yrs

 

[Kernal]

I would think if you had a crack all the way through the exhaust manifold that it should have a some carbon staining present.
Check further down the system around the flanges and Y pipe before the first O2 sensor.

 

[jonheld]

Just as I received my registration and smog requirements my chenck engine light came on P0172. System too rich.

From the FSM: