My 240 has become "chattery." The Bentley manual under engine noise troubleshooting says

High-pitched metallic tapping noises can indicate pre-ignition.

I don't think this is is, I run 91 octane.

High-pitched metallic tapping noises can be cause by a blocked flame trap.

I just replaced the flame trap filter with a brand new one

High-pitched tapping noises can be caused by excessive clearances of small light weight parts like those in the valve train. Often a simple adjustment will solve the problem

The noises do seem to be coming from under the valve cover. This could be it. Would this require a tear down of the head or removal of the engine from the car?

In a high milage engine (240,000 on mine), a light metallic rattle or chatter under load, accompanied by greatly increased oil consumption and smoking, may indicate severely worn or broken piston rings.

This is the best description of the sound I hear, but I do not have noticeable oil consumption or smoking. It's a '93 with a catalytic converter, could this be concealing this? It is non-EGR. I have not done a compression test, though I do have one. Perhaps that is why I should do?

I checked the ECU and it showed 1-1-1 for no stored codes, so that doesn't seem to be a problem.

It does have a very slight hesitation when it goes from idle to moving (starting from a stop sign or stop light). Could it be a problem with the fuel delivery system causing these noises. Like dirty throttle plate or injectors? Anyone think Seafoam would help?

Thanks in advance!