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I agree with you, but once we fix the axis override, it'll allow people to tune this way regardless.

Yes, but this is MANIFOLD vacuum, so if we had "negative" vacuum, we'd have pressure on the manifold side higher than throttle inlet side, and air would flow in reverse. What the ECU is seeing is MAP...

ETC Vacuum could not be negative in the true sense, though I see nothing clipping it inthe ECU so you could theoretically do so. Its the amount of pressure drop over the throttle. A negative pressure...

This blows up because the ECU thinks the throttle is between the manifold and barometric pressure.
Your manifold is now boosted, so its thinking it has to somehow get enough throttle area to flow...