Okay with the following info provided, what is likely causing the issue?

- Rough idle, but when turning the ac on the idle goes insane (rpm jumps from 600 to around 100 and back every few seconds)

- System too lean bank 1 error code. i.e too little fuel or too much air.

- P0421 error indicating that the warm-up catalyst efficiency below threshold.

- P1250 problem with the solenoid.


I have replace the maf and solenoid and all codes seemed to go away, except the car is still idling very rough, even more so with ac turned on , and the p0421 and system too lean codes pop up consistently

 

Check for vacuum leaks. These engines are common for a leaking intake manifold gasket.