Today when I was applying tire shine on my rear tire, I heard knocking sound from exhaust/muffler. Is that normal or should I get it checked? It sounded like two metals hitting each other, I thought my exhaust pipes were loose, but it wasn't. Do you have any idea as to what is producing the sound?

Also, I hear a humming/whistle sound when I'm crusing at about 70 mph or so from what appears to be from under the hood. The sound goes away when I'm not applying the gas. I have my intake resonator removed about a year ago, but it started to humming/whistle about a month ago. Have any of the people who have removed the resonator experienced this before?

Thanks

 

i have CAI.

mine's been "whistling" a little more than usual at highway speeds also..

i was thinking .

it might the weather.
winter..

or maybe the filter needs to be recharged or oiled or cleaned.

whatever.

i like the sound...imo.

 

You might be right about the recharging the filter. But what kind of whistling are you getting? I don't have CAI, I have K&N drop-in filter. Does anyone with K&N drop-in filter experience this before?