I'm assuming it's the same issue alot of others have, including myself; weak valve springs. I get random misfires at higher RPMs (6000-7000) and it is a result of weaker valve springs causing the exhaust valves not to seal quick enough causing some exhaust gases to remain within the chamber.
This is more common in K04 setups, but I see it as well on my tune with stock turbo.
Unfortunately, I hate to link to this but these guys had a good write up.
Most likely coil packs if you have higher miles or have an ECU flash on the car. OEM coil packs fail on flashed cars. If so check out R8 Coils to swap out and swap the spark plugs.