What would you do? #137 - Facing a ton of action on the turn in a multi-way pot

Full Tilt Poker $0.25/$0.50 No Limit Hold'em - 9 players
The Official DeucesCracked.com Hand History Converter

BTN: $57.90
SB: $58.80 - 15 / 11 / 27% steal / 5.6% 3bet / .9 aggression factor @ 568 hands
Hero (BB): $126.15
UTG: $53.95
UTG+1: $54.40
UTG+2: $96.05
MP1: $14.70 - 56 / 13 / 0% steal / 0% 3bet / .5 aggression factor @ 61 hands
MP2: $50.00 - 24 / 19 / 51% steal / 6.2% 3bet / 2.2 aggression factor @ 370 hands
CO: $50.00 - 20 / 0 / 0% steal / 0% 3bet / NA for everything else @ 10 hands

CO posts a big blind ($0.50)

Pre Flop: ($1.25) Hero is BB with Ad 6d
3 folds, MP1 calls $0.50, MP2 raises to $3, CO calls $2.50, 1 fold, SB calls $2.75, Hero calls $2.50, MP1 calls $2.50
I call because it is very likely MP2 is raising to isolate the limper and / or steal the CO's dead money posted blind.  This is a great multi-way hand.

Flop: ($15.00) Ah 8s 2c (5 players)
SB checks, Hero requests TIME, Hero checks, MP1 checks, MP2 checks, CO checks
I think about a lead here, but given my position, I opt to either check / raise or check / call depending on who is leading the action.  I get nothing though so we see a free turn.

Turn: ($15.00) 9h (5 players)
SB bets $11, Hero ???


Click to see results

Hero folds, MP1 raises to $11.70 all in, MP2 folds, CO folds, SB calls $0.70
Given that SB has a .9 AF, what could he be opening so big with that makes sense in this spot?  Clearly, he's scared of the hearts, but 2/3 pot on the turn?  This smacks of a set or Ace /broadway.  I'm beat.

River: ($38.40) 3c (2 players - 1 is all in)

Final Pot: $38.40
SB shows 9d 9s (three of a kind, Nines)
MP1 shows 3h Jh (a pair of Threes) - I think this is a very very marginal call for him.  Perhaps he's expecting another call or two behind him to get the correct odds?
SB wins $36.50
(Rake: $1.90)