we subarus call it a BPV (Bypass Valve). DV is so... VW. lol. but no, my BPV is not stock, its an aftermarket unit from TurboSmart. the thing is RTV'd to my intercooler lol. tried taking it off once, not happening easily, guess i should have thought that through more, but it doesnt leak. and ive had it installed for over 20k, just started happening last night.
anyway, its not a vac leak. when the car is surging, the manifold pressure is rock steady (i have a Defi boost gauge and ive tested this in cruise control) usually happens the most around 10inHg vaccuum.
tried going to advanced for a new sensor, they didnt have any in stock, and they wanted to charge me shipping (to the store) to have it by the 11th "maybe". yeah fuck that.