I have a nice buzz coming from under and forward of the driver pedals on my 2000 escalade. I put it up on stands yesturday and ran the engine where it usually buzzes, which is about 1500 revs. couldn't make it buzz, so i started tapping exhaust with the rubber malet. I thought it was the heat shield above the cross over which would be right in the areaof my problems, but it wasn't it. I did notice a slight buzz when tapping on the y under the O2 sensor. Took the sensor out, and the buzz seemed to go away. Anyone else ever run across this, or am i barking up the wrong tree?