Nismo180

Okay, I've got a SR20DET with the usual bolt-ons. S-AFC II tuned by torquefreaks. Was running like a champ until a little while ago I was out drifting with my buddy and on the way back if I went full throttle below 3k the turbo would spool unbelievably fast but even under boost it was bogging really bad like would have been faster off boost. Started developing crap on the rear bumper like it's running rich, it backfires and pops alot more. It runs alot worse in the morning when it's still cold and Every now and then once it warms up it will bog again like it did after the drifting. When it does do that it only does so after 25% throttle according to the S-AFC I'm thinking it's only during open loop mode and it's my o2 anyone concur?