Engine has a noise that occurs at valve rocker speed

First, I am wondering if you have found any further info in TSB's?
Second, I bought a stethescope. Listening in a number of different places on the engine, the heads have no abnormal noises. The timing chain area sounds nice and smooth, as do other places on the block. It is hard to get to the injectors, but thethree that are easy make a noise at the correct speed, which is not surprising, as they fire once per two revolutions. If I listen in a couple of places on the manifold, I seem to hear the noise.
My question is, is there a proceedure for testing the injectors? Could one of them be making an unusual amount of noise?
Thanks.

OK
In that case, is there anything else that will make a noise that is louder at the top of the engine than at the bottom, is louder with the stethescope on the manifold than on the heads, timing chain case, water pump, bottom of the block or any of the various pumps and alternator on the engine, and is really loud on an injector?
I would think that I had made a mistake of some sort with the lifters if the noise was any different after I had put new ones in, but it ain't.

I am having this same exact issue with my 1995 v10 3500 club cab off road. Trucks only got 110,000 and this is driving me insane. What did you ever discover it was? Really hoping for an answer this made my night been searching for months.