Vacuum leak?

[DJ1911]

2012 135i M-Sport, 5" FMIC, Catless DP, CP, tune

I got a bluetooth ODBII connector and using the Torque app I'm showing a steady 1.5 in/HG of vacuum at idle. Under firm acceleration, I'm topping out around 18 psi of boost, but as soon as I stop and idle I'm back to 1.5 in/HG of vacuum. I would think a vacuum leak that bad would make the car very weak off the line and should be audible with the hood up, but neither of those are true. Is this even possible?

[Edrift]

Torque doesn't read boost and vacuum accurately

[Petro135]

Try a boost leak detector. They are cheap and easy to use. Mhd is pretty accurate. Reads exactly what my boost detector reads for vacuum

[Jeff@TopGearSolutions]

Not sure how accurate the gauge is for idle vacuum.

You can just pull a vacuum line off at idle and see what really changes, then you'll know what's what.

However, you could have a small leak but a small leak wouldn't be that much of a difference.

Stock is 16-18. A small leak may show as 14, as an example.

[juld0zer]

Is 50mbar not the correct manifold at idle with a healthy CCV system? The throttle flap is adjusted to creat this vacuum at idle to provide enough suction to draw out vapours.