Well if it's knocking on the engine cover you can take it off, it's only held in place by one bolt I think then it just pops off, I took mine off then realised it was the airbox that was causing the
problem for me. If it's the airbox then it's a good excuse to buy an induction kit lol, failing that you may have to look at getting something placed between the brace and the airbox to dull the sound. I just for testing purposes wedged some rag in between the two just to confirm it was that which was making the noise. I'm not sure if it's possible to alter slightly the position of the box to maybe move it an inch or so to give you some clearance between the two parts.