That’s normal - to a point. With the engine off, the manifold pressure should match the barometer. Running at idle, the manifold is under a vacuum. As you open the throttle, more air goes in, reducing that vacuum, but it shouldn’t ever reach the same reading as the baro. Turbo mods will behave differently. At high throttle, you should see pressure above the baro (boost), but at idle, it would likely fall back to a vacuum, since there isn’t enough exhaust to spool up the turbo.
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