100NL: Nut Flush Draw in awkward spot OOP

[QuadLaser]

Betting villain is donk, like 40/3/1. Raising villain is quite aggro, 25/20/4 and has been making alot of action for the table.

Full Tilt Poker, $0.50/$1 NL Hold'em Cash Game, 6 Players
LeggoPoker Hand History Converter

UTG: $72.55
MP: $50
CO: $23.15
BTN: $115.50
Hero (SB): $118.25
BB: $244.55

Pre-Flop: 5[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/heart.gif[/img] dealt to Hero (SB)
UTG calls $1, <font color="red">MP raises to $2</font>, CO folds, BTN calls $2, Hero calls $1.50, BB folds, UTG calls $1

Flop: ($9) 9[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/diamond.gif[/img] K[img]/images/graemlins/heart.gif[/img] (4 Players)
Hero checks, <font color="red">UTG bets $6</font>, MP folds, <font color="red">BTN raises to $16</font>, Hero??

Whats the best move here? A call exposes my hand pretty bad...