Is the main spark advance ADDED to the distributor setting? Or is the distributor setting already accounted for, assuming the base timing is set correctly in the bin?

I ask this because my base timing is set at 4 BTDC. At idle the ECM advances it to around 10-11. I fail to understand why the ECM should be advancing it beyond the base timing just to idle right so I plan on setting the base timing to 10-11 (what the ECM is shooting for). So if I bump the base timing up by 6 degrees should I LOWER the entire spark advance main table by 6 degrees to create a nuetral change, therefore preventing the ECM from over-advancing the spark timing? Or just re-set the base timing value and let the ECM do the rest?

In other words: Does the ECM USE the main spark advance table directly, or does it SHOOT FOR the main spark advance table?

 

As long as your "base timing" in the Constants matches your base timing on your distributor, then the Main Spark Table will match the TOTAL timing at the distributor (ie. will already include the base timing). (Some older versions of TunerCat's $8D TDF did not though...)

Any "cold timing", "P/E timing" or "Highway Mode timing
" will be added to the Main timing though