[gulebjorn]

Well, you have 5 outs to make two pair/trips. So the odds against you hitting are 42-5 or worse than 8-1. You are getting 3-1 pot odds, so calling to improve is very -EV.

Of course, you have a 17% chance of hitting a four-flush too, but you'll still have to call extra bets to see a river with that. I'm not sure how to calculate it, but I don't think you can just count those 17% as 8 outs or something like that. I've seen 2 outs being counted for a backdoor flush, but I think that's more for an all-in situation on the flop. However, I am pretty sure that the backdoor flush can not make up for the difference between 8-1 and 3-1.

So IMO, your only real options are raising or folding here. I think a raise to $30 = 3/4 of current pot and 3 x original raise would be fine. If you don't wanna put that much in with a pair of 9's, I think you should dump this right there.