You don't want vacuum on the turbo oil drain/sump, only the suction to empty it if that makes sense, that's why venting it effectively is important so it sits at a neutral pressure, that is what your turbo oil seal wants to work with.

I run a element tuning dry sump kit, ARE dry sump pan, factory position oil pump(Cosworth high volume) provides pressure and an Avid 3 stage dry sump pump, 2 large -12 stages clear the engine sump and a little -6 stage was added to clear turbo sump. Its just like the Cosworth kit...but better, 1/2 the price and the Avid pump runs in the AC comp position and uses the AC belt, not some bulky retarded gilmore drive addition.

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MY99 WRX EJ2.35L 720whp 9.48@147mph
https://youtu.be/c_lYEG0_Dyo