P0418 code

Yes, I have just performed a lot of work in regards to different codes, which forced me to wind up replacing the PCM. At start all other codes are gone, yay. The engine starts then shuts down in seconds. I see that a PO418, the only code reading, references the ASD relay circuit. The relay is good. I did though snap one of the vacuum lines from the air pump which I pitched with electrical tape temporarily, seemed tight. I disconnected the unit few times. Now before I tear it all apart is it more likely
a vacuum leak, dinked ground, blocked tube, or malfunctioning air-pump.