Missed AK or Flush Draw, or does He Have the Goods?

[Jbrochu]

PokerStars No-Limit Hold'em Tourney, Big Blind is t50 (8 handed) converter

$30 + $3

UTG (t895)
UTG+1 (t2910)
MP1 (t1325)
MP2 (t2150)
CO (t1290)
Button (t2490)
SB (t1370)
Hero (t1070)

Preflop: Hero is BB with 5[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">3 folds</font>, <font color="#CC3333">MP2 raises to t100</font>, <font color="#666666">3 folds</font>, Hero calls t50.

I will usually call in this spot since I still have 20x BB and am getting more than 3-to-1 odds not counting the implied odds if I flop my set.

Flop: (t225) 9[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/club.gif[/img], 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>

<font color="#CC3333">Hero bets t225</font>

I'm usually of the "no set, no bet" mindset, but this looks like a pretty good flop to take a pop at. In hindsight, I probably should have bet t150 to t175 to gain the same information. Does anybody routinely check fold here?

<font color="#CC3333">MP2 raises to t2050</font>, Hero....?

This smells strongly like the either the missed AK or flush draw. Of course, could be a bigger PP or trips afraid of the flush draw and I'm already beat.

Pot is offering nearly 2-to-1 odds. What's your move, and is it even a hard decision...?