I have a 2000 GTP with 185k miles. It has developed an engine noise that makes an "ERCH" sound about every 1.5 to 2 seconds at idle. the noise will speed up when the RPM is increased. The noise seams to be coming from somewhere around the #1 cylinder to the middle of the intake. I have taken off all of the belts off and started the engine and it makes the same noise. I originally thought it would have something to do with the timing chain since the noise frequency was slower than engine RPM speed. If it was a bearing I think it would be a lot faster or continuous. Any help would be appreciated.