If its got some carbon buildup you can try Kreen from kano labs.com
they also make some other great stuff, and the BEST penetrating oil around Aerokroil, blows away PB and the others

Aaron

 

Aerokroil was brought down by the aliens along with microwaves and computers. Lol. Yes, it definately is the best stuff out there.

Sorry for not being on topic. Seafoam will definately help out if you have carbon buildup in the engine. If thats contributing to your knock or not is beyond me. I dont know much about KR and how to solve it so Ill leave that up to other more knowledgeable members. I do know that the filter under the hood wont help the situation. A FWI will help bring in cooler air into the engine.