[bigpooch]

You won't be far off if you muck every straight draw when
heads up out of position; even with KQJTx against a button
raise, although you have some chances of winning by pairing
up, you might be up against AA or 99 which really cuts your
chances of making a straight. Also, even if you make a
straight, on rare occasions you might run into a bigger
hand.

The biggest factor is the opener's range. If you had a very
weak flush draw with no chance of winning even if you pair
up on your highest card, unless you can expect to get paid
off almost every time, you are better off folding. If the
raise came from early position, you won't be far off if you
mucked everything except a straight flush draw or an ace
high flush draw (without a king in the hand). If the raise
came from the button, and his range is approximately 99+,
you won't be far off if you played almost any flush draw.