I would like to change air filter in my Octy2 vRS, is it anything what u can recommend ? Something what can give me nice sound and performance .

you need to speak to someone like bahnstormer he will know more about that. i could tell you whats available forh a petrol vRS, but im not sure on the availability of tdi intakes.

Tough one to call with it being diesel. For optimum results, you would need a full cold air induction kit to avoid heat soak. Possibly a modified MAF if airflow went outside of normal limits. So £7 for the OEM filter, or £xxx to get a bit of induction noise and possibly slightly better MPG.

Better MPG ??

Better performance - You're as likely to decrease it as increase it, choose the wrong item and you'll be pulling in hot air.

Noise, depends as you would need an induction kit to substantially change the noise with just an air filter and as such an exhaust might be better. The induction kits are much more likely to be affected be heat soak unless you get one that directly pulls in outside air. If you do this you however increase your risk of pulling in water into the engine in bad weather.

MPG, this will be the same with all filters if you keep them clean MPG is good, let them get dirty and you have issues.

Personally I go for changing the paper filter every 10k miles, but otherwise you could look at an EVOMS system.