Tapping/knocking sound

[Lonestar10]

my truck has right at 28,000 hrs with 1,031,000 also has an APU,

Update on this issue.

now that truck is demandated...i can hear a miss or burp in the exhaust note when idling and accelerating before the turbo fully spools. need to see if my mechanic has the cummins injector leak test tool or if i can find someone on here to 3d print one for me.....

truck runs on single cylinder test so this is the last test i can think of to try. when previous owners overhauled it they only put in 1 new injector now i need to get ahold of Intl and find out which one.

called cummins 6300 after core returns for 4 actuators and 6 injectors...damn highway robbery... so ied wrather see if i can find the problem with the tool.