Help!! Exhaust leak or something else?

[NoOneIsPerfect]

I got s13 FB w/ apprx 150K on KA24DE.

While I was driving, all of a sudden I hear similar sound like backfire when I release gas anywhere from 2500rmp and above on all the gears. Since I live in an apt, and got no light to take it apart tonight, I can't start looking at it till tomorrow morning.

Everything is stock for now and except for no heat shield (previous owner took it off?).

So the question is... could this be a exhaust hole, gasket problem or something else?

It sounds like it's coming from ex mani area but not too sure since I am dead tired and didn't wanna rev up my motor and get a complaint from my neighbors!!

Any educated guess? Similar problems? Timing chain was already clicking but I don't think it sounds anything like timing chain problems. Though I did already order replacement parts.

Thanks!