I would never use any oil additives, this engine already call for synthetic oil, which is all you need to to keep the engine and the turbocharger properly lubricated.
You CANNOT use anything but VW/Audi approved engine oil, which is synthetic oil, ANY other engine oil will kill the turbo and the crank vent system. NO VALVOLILNE ever. The right engine oil will have the words, meets VW/Audi specification 502/505, right ON THE LABEL! Mobil One 0W-40, Pentosin, Wolf's Head, and a handful of others meet those needs. If you have been FOOLISH enough NOT to use the proper oil, you WILL require a motor flushing. The German's make an excellent one from Lubro-Moly. TRUST ME, i have SEEN vw engines self destruct, and have rebuilt them. There is only ONE additive I recommend , and you will trouble finding it. It comes from GERMANY and is called CERA-TEC. It is liquid ceramic. But it can ONLY be used when the other conditions are met. Your VW engine is MIRACULOUS and has piston squirter jets built into it. PLEASE read your manual and STAY totally AWAY from wax based engine oils that will eventually destroy your cam adjusters, and timing chains, and timing belt mechanisms. If you have NOT been using the proper oil, have your turbo oil feed and return pipes cleaned out with SEAFOAM or AMSOIL foaming cleaner. GOOD LUCK!!
There aren't too many additives of any type I would recommend. If you do use one, then read the instructions as to how to use it and follow them; more is not better! I saw a ford pick up a person put in 6 quarts of STP. locked up the engine when it cooled down, had to take it all apart and clean it out. The best thing to do is keep any and all fluids clean and fresh. Gas treatments only foul the spark plugs, tranny additives only ruin the seals. If you end up using it, put it in when the engine is warm and drive it for a while to mix it up.
well I have one and i use it alotand i have to go get trims more often cause it damages the hairand causes split ends