stumble at around 3k rpm

What mobile transportation unit is this? You can find knock sensors on here on the cheap.

Check your hall sender connection if it's a 10vt.... Had a loose connection that would cause a miss or stumble.

95 audi s6 20vt, was told that the cam sensor or the knock sensors could be the problem. getting code 2413 (Blink Fault Code), 00561 VAG1551/2 Fault Code Number
Mixture Adjustment,
Adaptation limit exceeded, Adaptation limit not reached, Leakage in exhaust system before 3 Way catalytic converters, Incorrect signal for Mass Air Flow Sensor, Spark plugs, ignition coil(s), or Ignition Coil Power output stage malfunctioning
Symptom: Rich mixture, increased fuel consumption

You check for spark? plugs, cable, dist...check coil (bently?) Fuel, and compression first? I know its basic bullshit but I got wrapped up with similar intermittent probs and it turned out to be a faulty throttle sensor that seemed to be unrelated but checking the basic diagnostics shoved me in the right direction.

I'm just sayin don't throw a buncha feckin parts at it until you know its not something staring you in the face.

Likely a pos or coil issue.