Tapping/knocking sound

[Lonestar10]

Cm871
I have a a tapping sound only heard with window down. I would compare it to marbles hitting each other or for some older generations a teacher tapping chalk on a chalkboard. Made sound before and after demandate though it seems less prevelent after demandate with the minor changes in timing.

Only happens under load I can't recreate it stationery it's about 1/2 speed of the engine so exhaust or powerstroke. My mechanic thinks possibly an overfueling injector. Truck runs strong but the sound makes my skin crawl. Passes cyl cutout runs on 1 cyl on cylinders the same, cyl perf test, and the 15 sec crank test.

Can't really move actuators if they are causing it as I can't tell location. And at about 500 an actuator or 600+ an injector I don't want to throw parts blindly.

Engine has 150k on overhaul only 1 injector was replaced during overhaul by the intl stealersh!t. Before I purchased.

Thanks in advance for any recommendations.