Ok, i think i figured it out. The SMC will correct all map values all the time. The only time it will tell the ECU that the MAP voltage is at 4.5 volts is at your max boost pressure. You use the adjustment screws to fine tune the duty cycle( MAP voltage). So stock non turboed, the map voltage is at 4.5 volts at WOT (0psi). Now with the SMC on, and running larger injects, the 0 psi map voltage may be only 2.5 volts going to the ECU, so the euc shortens the duty cycle to make proper A/F. Now when we go under boost, the map voltage increases over the stock 4.5 volts at 0+ psi on up, then the SMC will max out the output map voltage at whatever your max boost is, to which you adjust it on the SMC, using the 4 adjustment screws. So lets say we are running 10 psi. At 0 psi, the map gives the SMC a voltage of 4.5 volts, the SMC corrects this to lets say 2.5 volts to make the proper mixture. Then when under boost, the map goes above 4.5 volts, and then the SMC will increase the output voltage going to the ECU to its max of 4.5 volts under max boost. This all would work assuming our map's can increase voltage above 4.5 volts in a linear fashion. I've heard we have 1 bar map sensors, which equals to around 14-15 psi.

13.5 @108 MPH-2.2 60ft(stupid FWD!)
S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential
fuel injection)
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-1998 Mitsubishi Eclipse RS-T- "Toy"
-1992 Plymouth Laser Turbo AWD(SOLD)
-2000 Honda CR-V(daily)