Drill out the sample hole and solve that problem.

The test works by blowing though a 0.5mm or something hole and measures the current on the blower motor to establish what back pressure generated from the "known hole" then it pressurizes the tank and compares.

If you have a smoke tester you can prob figure out if you actually have a leak somewhere.

Possibly just open your tank to vent right away when to stop to sea level to get it to baseline?

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)