I’m not sure you’ll get a CEL from venting to atmosphere, you’ll just be running rich by the amount of air that’s vented. This probably isn’t a big problem, but you will be increasing lag, as you said.
Boost pressure is measured way downstream from the DV, so any leaks / better sealing would only be noticed if you weren’t meeting or are now better meeting boost target. You’d be able to tell that from logs, but not from dyno or butt dyno.
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