CAT 3406E Strange boost sound and clacking sound

Hey guys i have a 98 volvo with a good old cat E motor 1LW to be exact... i recently did a rebuild about 70k ago i was told the head was rebuilt everything was fine until recently i started to notice when i hit boost from 0 to about 20 psi the turbo doesnt have constant whosh shound it has a an interruption anything above that you cant hear it makes 32-34 psi doesnt misfire the power is there its really strange... also whats more alarming i can hear what shounds like clacking/ticking coming from what i think is the left top side of the motor you can only really hear it if the motor is warm... so i went back to the guy who put it all together we changed all the injectors thought it was a bad spring nothing same issues then went ahead and checked the front timing gear lash it was a little tight the mechanic said when he tried to take out the gear it was hard we set it at 10 thousand still nothing then we swapped the ecu for giggles since i have a spare ready to go nothing.. another issue that im not sure if its connected or not is that i sometimes get a misfire if i say start at 1000rpm and i go half throttle or more in the lower gears its hard to replicate its not a constant miss and thats also after the new injectors... im out of ideas the mechanic says he went over all the top end of the motor and its all good rockers and all he even says he measured the valve height but im starting to doubt it all and have a feeling i got taken for a ride and the head wasnt replaced what do you guys think?... whats a good way to diagnose this clacking noise? its only present under load idle is fine oil pressure is 70 rolling at 65mph

 

I really appreciate the reply thats a good idea I'll check into it later on today... I was more concerned with the clacking noise coming from the left side of the motor and I thought they might of all been related to each other... any idea what the clacking might be?