4.7 injector "chatter" question

Recently I began to hear chatter from the 4.7L motor in my '01 Dakota. After researching this morning I have discovered the noise is on the fuel rail. The noise only occurs at initial startup for a few seconds, upon initial acceleration from a stop, and I can get it to "chatter" at idle if I rev it up then let off the pedal it will chatter for a few seconds.

Is this what happens when injectors get old? The truck has 172,000 miles. Can a fuel injector cleaner help reduce this noise?

Put a fuel gauge on it. Does it fire right up? or crank for 10-20 seconds? Our you sure its not a valve or timing chain rattle?

The truck fires right up and runs great except for this noise which I thought for sure was a valve type noise or now that you mention it seems like it would be a worn out timing chain; however when I use the mechanics stethoscope these things sound fine. The noise is very loud when I put the probe on the fuel rail. When I put the probe on the heads, block, accessories, etc. everything sounds fine.

Maybe the fluid is just able to pickup and amplify the noise which might be created elsewhere; however with the probe I can only detect the noise on the fuel rail. I am going to try a fuel injector cleaner to see if it helps.

I do have a fuel pressure tester so I will test the pressure.