my buddy has a built truck running a A5000 , the truck idles and drives just fine but as soon as he gets on it and little bit, and is up around 50-55ish psi there is a loud kocking/tapping sound comming from the motor could this be caused by stock vaulve springs?

 

you need to tell us more about your buddies truck, does it have studs? stock injectors? what all has he done to it?

from what you have told us already, it doesnt sound like the turbo is wounded, it sounds like the motor isnt happy

hope this helps

 

Like Will says if that thing is knocking under high boost I would be looking for at least a boost leak, valve lash, inspecting turbo, etc. for an issue.

 

its fully built... dual cp3s, huge injectors,full billet trans,apr studs etc etc etc... but hes got stock vaulve springs and a stock head..