M54 2.2 low rev engine knocking

[landugong9990]

Hi n good evening fellow friends n otais.
Two months ago,i bought an m54 2.2cc.
There's a noticable sound of engine knocking at low rev when i wanted to floor the throttle.
Is this normal for the m54 engine?
I assumed it is due to vanos about to engage.
I cleaned up the air filter already but didnt replace it.
Using ron95 since a fren driving e46 also uses ron95.
Thank you in advance for any replies.

 

[Herbert]

Check your catalytic converter as I had experienced similar low knocking sound with my e39 m54. The materials inside the cat converter has gone brittle & disintegrated hence causing the sound whenever you rev the engine.

 

[landugong9990]

Check your catalytic converter as I had experienced similar low knocking sound with my e39 m54. The materials inside the cat converter has gone brittle & disintegrated hence causing the sound whenever you rev the engine.

Ic....so can i dismantle the catalytic n replace it with a normal middle silencer?