you should hear the turbo spool up. know i do agree that under light to no load youw il not hear it. and even under a moderate foot its not that loud. know if it were chipped its loud. and spools up faster. most i seen out of my early 99 stock was about 18 and that was pushing eth pedal to the floor. know with a chip i am easily seeing 29 psi. does teh truck sound strong drive strong. ask him if you can pull teh intake tube off and grabe teh turbo blades and look at them closely and check for up-down and side to side movement. just some things to check. might be worth a few buck for a dieel tech to look at like your own mechanic. just my 2 cents though