I wonder if someone can help me. Engine is making a noise that sounds to me like an air leak in the intake. Noise increases with engine load. Mech checked engine with stheoscope and determined noise was coming from either serp. belt idler or timing chain. Car is 04 3.0L 74K. Mech tried lubeing pulley and said sound intensified. Is there anyway to check for streched chain{pass side} or decreasing tension on belt to determine whats at fault? Noise does not sound like a failed bearing more like the chain rubing on the guide. Thanks for any advise in this matter.

The idler is pretty easy to eliminate as a suspect. Remove the accessory belt, start the engine, and see if the noise is still there. It should be safe to run the engine for a minute or so without the water pump, but it will probably only take you a few seconds to see if the noise is still there or not.