Playing OOP w/ 99

[BGnight]

MP is kind of a standard 21/16 TAG. CO is a 15/11/2 nit. How often do people lead here in this spot? What do we do on turn when CO calls? I'm never sure how to play this hand in this spot. When CO call flop I figure there's good chance he has a J, but could also have smaller pr/flush draw.
PokerStars No-Limit Hold'em, $2 BB (6 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

saw flop|<font color="#C00000">saw showdown</font>

MP ($226.05)
<font color="#C00000">CO ($291.80)</font>
Button ($93.50)
SB ($40.10)
<font color="#C00000">Hero ($368.20)</font>
UTG ($54.25)

Preflop: Hero is BB with 9[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/heart.gif[/img].
<font color="#666666">1 fold</font>, <font color="#CC3333">MP raises to $8</font>, CO calls $8, <font color="#666666">2 folds</font>, Hero calls $6.

Flop: ($25) 4[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $18</font>, MP folds, CO calls $18.

Turn: ($61) 7[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">
Hero?