[boostedc10]

What he is referring to is the problem the 4l60e has with the AFL valve bore. What can happen in layman's terms is the bore of the AFL wears out causing an internal leak / loss of pressure. With this internal leak the EPC cannot create the pressure needed (because it is fed by the AFL valve) to move the boost valve, which in turn causes low line pressure all around.

Typically though when this is the case you will have faults for the shift solenoids at minimum (but not always if the bleed off is low).