Question about knock at high RPM

[rehirsch8]

I have an 04 coupe that was tuned last summer with a Magnaflow exhaust and Z06 airbox. It's been running very well. Recently I upgraded the airbox with a WCC Hurricane system. The power has increased but I noticed some knock (not alot) at 5500 RPM.

Any suggestions on how to get rid of the knock. One of the changes the tuner made to the ECM was setting the air/fuel mixture to just over 13. Does this need to be re-adjusted?

Any help is greatly appreciated here.