why are you 4 betting 99 in position? If you are ever going to 4B 99 in this situation it has to be in an attempt to get everything in preflop. As played fold, but keep your 4 bets to hands you are very happy stacking off preflop (and on most flops) and complete trash where there is no value in seeing a flop.
Villain could be shoving a tp type hand because he is scared of you having the Ad or something, or villain may very well have the Ad and just shoving and trying to fold out 99-QQ etc. Even if villain has 2 overs to you, and the flush draw you are in pretty bad shape (but getting odds
to call). But this might be a retardedly played jj/qq with a diamond etc.
Anyways, calling this vs an unknown is spew i think. Change your hand into 72o w/ no diamond, and you basically have what your hand is worth on this flop, only now it doesn't look so pretty and would be alot easier to fold . Just don't 4B this preflop, makes no sense at all vs somebody who is 3 betting you for the first time when your hand plays so well in position after seeing a flop.