Normally, when I view my sensors through torquePro, my MAP sensor shows 0.0 to 0.3 psi BOOST at idle. Today I noticed that it showed 3.5 mm/Hg VACUUM at idle.
Even showed the exact same reading with key-on, engine-off.

No drivability problems, no CEL code indicating a bad MAP.

So, whats going on here? Bad MAP sensor?
Or is it my current altitude?
I'm not in FL today at 50 ft above sea level.
I'm in the CA high desert at almost 4000 ft.

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U.S. Army Retired

You guessed it - at one time production vehicles intended for altitude service required recalibration of the carbureted systems - cars bought down lo and driven hi, or cars bought hi and driven down lo were at times untractable without recalibration - flatlanders driving thru hi mountain passes often noted less than spectacular engine operation - EFI has solved that problem, at the very least

Pay attention to that reading and you can quickly spot a dirty air filter

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'05 CRD Limited
Pricol EGT, Boost
GDE Hot '11; EDGE Trail switched
SEGR; Provent; Magnaflow;
Suncoast T\C, Transgo Tow'n'Go switch;
Cummins LP module, Fleetguard filter, Filterminder
2.5" Daystar f, OME r; Ranchos; K80767's, Al's lifted uppers
Rubicons, 2.55 Goodyears
Four in a row really makes it go

Mine reads like 2 psi at idle on Torque but I always just thought the turbo was spinning at idle. I guess i need to offset it.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

Considerinig that GDE modified BOSCH ECM programming to meet EPA specifications, and they recently stated that EGR is used for ~1min after startup, look at the values during startup and idle - should indicate if any offset is required - might be a good idea to post the numerical values for posteriority...............

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'05 CRD Limited
Pricol EGT, Boost
GDE Hot '11; EDGE Trail switched
SEGR; Provent; Magnaflow;
Suncoast T\C, Transgo Tow'n'Go switch;
Cummins LP module, Fleetguard filter, Filterminder
2.5" Daystar f, OME r; Ranchos; K80767's, Al's lifted uppers
Rubicons, 2.55 Goodyears
Four in a row really makes it go