I swapped out my old electronic Greddy analog -30/30 boost gauge for a new AEM -30 /35 digital boost gauge today and I noticed some inconsistencies between the two. The AEM unit seems to be reading 6-7 psi below what the Greddy unit was reading. I am more inclined to believe the AEM to be more accurate, however it is displaying my idle at -17/-18 inHG and max boost only hits 21 psi. My Greddy unit would read -10/-11 vacuum and max boost was 27 psi, which is what I was tuned for using the Greddy unit. Having a 2.3 and Cosworth M2 cams, -10/-11 seems to be a bit more realistic after doing some researching, it seems to be consistent with others with similar builds. And the previous power levels I made at 24 psi seem to be consistent with EVOs with similar builds.
There are no kinks in the vacuum hose and it is tapped into the same location, off of the fuel pressure regulator, but the vacuum hose length went from 6 inches from the Greddy electrical wired sensor to about 2.5 feet to the AEM wired sensor.
The AEM unit is using the same ground as my AEM UEGO wideband and they are both tapped into the same power source, off of the ignition. This is exactly how my Greddy unit was wired. I'm not sure if this could be causing a problem for the AEM unit, but I'd like to be sure before I have to cut and re-solder my connections. For what it's worth, I ran my old AEM Tru Boost and AEM UEGO wideband off the same power source and ground on my previous EVO without a problem.
Something else I noticed was that the AEM unit sort of stops at 0 psi for a split second before climbing into positive numbers. With the analog gauge, it would gradually increase without an issue. Digital boost gauges are generally more accurate than analog gauges, but a difference of 6-7 psi seems rather excessive. Unless I've just been wrong this entire time and the Greddy gauge was just that far off. I'm just not sure which one to believe.