I think you misunderstood- Scan Tool spark advance
Base timing is 8-10*
2000 rpm #1=19-20.1* #2= 28*
3000 rpm #1= 40.1* #2= 40.1*
Used a timing light on #1 @2000 rpm & see 28* on crank???? not 20.1*
The MAP is used and read but cannot adjust fuel based upon BOOST. The ECM doesn't allow it, only the MEFI-3 does.

Yes, I think the IAC is maladjusted & will adjust it asap.

Per Jim Shoffner-Az speed. The merc ecm's MEFI-1 is pretty sloopy in regard to timing. If there is an rpm difference at around 2000 rpm, the ecm has "slots" to set timing and may indeed allow that variation. He also wanted me to take some MAP voltage readings at speed and report to him. He also believes the IAC & TPS as well as the throttle blades need to be readjusted. He is sending me the values with my ECM's. He did make a couple of adjustments on them to help out, but with the new MAP readings, we will have to redo them again.

Just to ensure that we are on the same page here;
The scantool based advance values (19-20.1 and 28.5(I think ,very small text ))in your table pertains to 2000 rpm not idle as it shows in the table. Further you have 40+ degrees on the scantool at 3000 rpm. Do you have any scantool values for idle?

Then going to the values measured at the crank, they show 28 for both engines, both at idle and at 2000 rpm. No values at 3000 rpm. do you have any values at 3000 rpm?

Ok now....
@ idle the spark advance reading oscillates so rapidly both + & - that you cannot get a value there on the scan tool in normal mode. In service mode @ idle it is 8-10*... this is normal per Az Speed.
The crank timing is 28* @2000 rpm. The crank balancer is not degreed that far. I purchased timing tape to install this week on both engines. I can tell it advance quite alot though. Also, Az Speed sez that is not to much advance in an "unloaded" test. Loaded it will be much lower. I will find out!!