First off, you can not set the timing is ANY codes are stored in the ECU. Make sure it's clear first.
Second, base timing is 10?BTDC, not 15?.
Third, with the diagnostic jumper in place the ECU runs by a very strict base timing map; Out of diagnostic mode many factors cause shifts in the timing and timing is at no point static (in other words it's constantly changing).
Fourth, turn the car OFF before removing/inserting the diagnostic jumper. Trying to switch back and forth while the ECU is powered may yield unpredictable results or even cause damage to the ECU.
Fifth, the vehicle needs to be up to normal operating temperature before setting the ignition advance.
Sixth, have you verified that the mechanical timing is correct?
Seventh..... There's nothing I hate more than fixing someone else's poor swap... Welcome to Hell.
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