If it knocks at idle and gets louder with RPM, it is most likely a main bearing/rod bearing.
On cold engine, remove serpentine belt and run engine for 30 seconds, if knock is there then it is internal engine, if no knock, then it may be supercharger.
Blowers don't normally knock, they whine and it gets louder if bearing is bad, but anything is possible.
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Monday, June 8th, 2009 AT 7:41 AM