2006 Jeep Wrangler

I recently purchased a well cared for 2006 Jeep Wrangler, 4.0, 6cyl. Infrequently the cam sensor squeals. The noise stops at slight increases in RPM’s and when the engine is warmed up. The local dealership advises me there been no chronic problems with the sensor even though the last owner appears to have drilled two vent holes in the cover. Has anyone experienced a similar problem and is there a reliable solution?

How exactly does a cam sensor squeal, sure it isn’t your drive belt? Two holes were drilled in what cover, the valve cover?