Random boost loss and clous of smoke auq 1.8t

Hi guys newbie to golfs bought as project for me and son , every now and then i seem to lose boost and get a cloud of smoke from exhaust clears up after about 15 seconds then ok for a while. Changed pcv and hockey puck at a loss any ideas

 

These cars are getting on in age and it might be that time for the turbo to require a refurbish or the valve guides on the exhaust side might be worn.

What is the mileage?

 

yes

started to think turbo it has done 108k. thanks for your reply

 

Turbo or exhaust valve guides, or both.