Fuel injectors do exactly what their name suggests, they deliver fuel into an engine's combustion chambers to be burned. Fuel injectors can cause a whole host of problems that can lead to major engine damage, if not diagnosed and replaced or repaired as soon as possible. A dirty or faulty fuel injector can cause engine problems such as misfiring, hard starting, stalling and hesitation.
If you are hearing other noises, such as clanging or high idling, you might want to check other areas of your fuel system. ECS Tuning has a wide variety of products for your system, so be sure to look it over for the parts that you need.
* This part is designed for the TSI engine only. This can easily be found on the engine cover of your 2.0T VW/Audi. It will clearly be stamped TSI or TFSI.