Negative LTFT at idle

Stage 2 Stratified tune with high flow catted downpipe, 3" catback exhaust. Cobb Accessport is showing LTFT of 0.88 at idle with STFT floating around 1.00. LTFT gets up to 1.00 when accelerating, but quickly drops back down when coasting at stops. What problems should I be looking for?

+/- 5 is actually ideal. I think +/-15 is considered "in spec" iirc but closer to zero the better. If you have a big boost leak or something you'll usually see it go to like -20 .