Back fireing and power loss

[ezlnh8u]

Hello, I have a 1991 e30, I was having idle issues a few weeks ago, I ended up switching the idle control valve, did not fix the issues, my idles were at 3k on neutral, I ended up purchasing a used afm, that put my idles back to normal,
But a few days ago, I have been noticing allot of backfiring when I come from a high rpm like 3rd to neutral the exhaust pops and rumble, or if I am going down a hill on 2nd its popping,
I have switched the afm twice, all the plugs, wires look intact and not brittle, I also noticed that when I jump on the freeway the car seems as it wants to go faster on take off but I feel a slight hesitation, could it be a bad injector? thank you all in advance.

[ezlnh8u]

What symptoms would a vac leak show?

[ezlnh8u]

I tried the search option, but alot of the finds are for swaps, mine is stock.

[ezlnh8u]

Ok. anyone have a clue, what this could be, at high rpm going down a hill, the car back fires really bad, on the highway it drives smooth, I cant figure this out, I just ordered fuel injectors hoping that could be it, not sure if it can be the o2 sensor.