Secondary Air Injection Veterans needed

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I attempted to diagnose my P0410 and P1411 codes today with no luck.
I have cleared the codes and they always come back within 1-5 cold starts.
All components in the SAI system seem to be in great shape; the rubber is still soft with no signs of weathering or cracks and the plastic lines are still flexible and not brittle.

Here is what I did:

1) Disconnected vacuum line at yellow arrow, good vacuum.

2) Disconnected vacuum line at green arrow at cold startup (air change-over valve #2), good vacuum.

3)Disconnected air change-over valve (#2) at red arrow and checked for airflow at cold startup, good airflow (not crazy airflow, but with thumb placed over hole with light to moderate force, pressure would force air out in 1-2 sec).



I really don't want to go blindly replacing things, so I thought I'd ask a few questions:

1) could non-return valve #4 be blocking airflow? Is there any way to remove it from #5, or does #5 have to come off? I guess I could just check #4 by blowing into it...?

2) what sets off these codes (what detects that the system is working and air is flowing into the cylinder heads) and could it be malfunctioning?

3) could valves #2 and #3 be working only partially, causing reduced airflow and does the airflow at the red arrow on #2 that I reported above seem about right?

4) could weak vacuum cause valve #2 to not fully open (is it a variable, or on/off valve)?

Thanks in advance!