A lot of tappy noises on a cossie are normal when first started, but should(mostly) settle within 10 seconds or so, though there will always be one lazy one.
Some people have used pattern lifters, as some PUG/VW/SEAT and other ones physically fit, but operate on a different pressure so will never work well and cuase noise after a few hundred miles that won't go away, not worth it when the cossie ones are only around £75 a set, and easy to do as well.
I personally use a flush before every oil change, I only use WYNNS, as found it to be ace, it is not crude like the old flushes and disolves the carbon rather than causes it to flake away and block oil galleries.
It will not affect the turbo in any way, quite the opposite as it will clean the oilways there too.
If it only taps when it is cold but ok when warm, I would not worry, mine has chronic piston slap when cold, and people mistake it for a MASSEY FERGUSSON, though at 170,000 miles without rebuild it is entitled to a protest now and again!!
I use flush in new engines as well, the insides of other engines I have taken apart which have been flushed regularly show NO carbon deposits, not a trace anywhere, turbo engines are by thier nature going to suffer far more blow by than non turbo so causing more carbon wash into the oil.
Just use a good oil like SILKOLENE PRO S, or similar to help keep it clean as the detergent package is great with this oil, and get it nice and hot once a month or so as this also helps to rid the oil of crap.
tabetha