hard to say cos i've never seen the .82 rear on the gt2871r.
I know on my gt2871r T28 with .86 rear , it starts to spool at about 2,300k, then hits 10PSI at about 4,500k.

Haven't seen a gt3076 on a b16, but it would be at least another 500rpm later

Judging by my compression and a 8.6 i'd say it would take another 250 to 500rpm more to spool up + 500 or so to boost to 20PSI. Once you get about 6PSI the boost will jump very fast.

that's my best guess