If I'm flatting 999 I'm likely not folding any turn card, regardless of what it is. Calling all turns and re-eval river.

If villain has spades, he'll probably bluff a Q/8 turn, if villain has Qx or 8x he'll probably bluff spades etc. So for those reasons, plus the strength of our hand and the equity we have vs hands that do happen to out draw us on the turn, i'm never folding turn.