IIRC is one of the 1st signs of the banjo filler bolt getting plunged. Pull both bolts, inspect. And go from there. One in front DS head & the 2nd, rear PS the feed the turbo. If clean, the AVCS need a good cleaning or replaced.
Original Motor/VF-40 Turbo/15k OCI, Amsoil 0w-30 SSO & Ea. oil filters. Tuning Alliance Stage 2+, 18.5psi. Member; 300K + club. Currant mileage:302980