Detroit s60 thumping/knocking noise under boost

i got 2009 Detroit series 60 14L Ddec VI in WESTERNSTAR. recently the truck started making like thumping/knocking noise under boost.mostly between 20-33 PSI.it gets really loud when turbo is spooling up.it is VGT turbo.when i feather the throttle and the boost drops while the rpm's(1300-1600) stays the same the noise goes away.soon as the turbo spools back up the noise comes back.i replaced the turbo & the CAC (DURALITE) about 56000 miles ago. i read somewhere while back that little bit noise is normal for VGT setup but this is really loud.i checked all the clamps, turbo piping and the boots everything looks good.no play or damage to the turbo shaft either.no loss in power or fuel mileage.its not getting check engine light but its is logging code PID-103 FMI 0 for Turbocharger #1 Speed.anybody know where i can start to diagnose this problem?

 

i did that.no free play of the shaft beside the normal.no broken fins or anything else.

 

i did do regular PM on it.so ill recheck the fuel filters to make sure they are put on correctly.

 

I checked all the fuel filters everything is good.

 

Yes