Msd pro billet in a small block 360 backfire at idle

gap is fine (.018-.030) are the pickup wired polarity correct? polarity issue will trigger the falling edge instead of the leading edge, and alter timing. IF you checked the wires to the manual, not the issue then unless programming is changed? 1000 RPM rotary switch position
Magnetic Trigger (Falling Edge) ON 187mJ 4
Magnetic Trigger (Falling Edge) ON 145mJ 5
Magnetic Trigger (Falling Edge) OFF 187mJ 6
Magnetic Trigger (Falling Edge) OFF 145mJ 7

Maybe try the other setting to see if it changes anything.
Pertronics calls out points/electronic and magnetic as 2 different settings...