Oe = Original equipment
Bpv = By pass valve i.e. blow off valve
Crush = Crush with whatever blunt object you prefer. As MF-DIF stated below generally a hammer but a vice is better.

This quote speaks about Dsm(s) but the principle is the same:
"Owners of highly boosted cars have discovered that the stock 1G BOV tends to begin to open too early. This causes a pressure leak in the intake system that limits boost. The valve tends to leak somewhat at lower boost levels, then opens fully when it's supposed to. This low-level leakage is the problem. "

So by crushing the stock bpv you're limiting how much it'll open, which in turn will allow higher boost levels.