The map voltage will fluctuate when under vacum conditions. At WOT, it should read 4.5 volts or very close to that. Basically at 0 psi, 0 vac, it should read 4.5 volts. Boost shouldnt matter on what voltage it reads, as you should have a fuel cut defensor of some kind to keep the voltage no more than that.

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)