I tried that stuff on an early 2002 Ibiza 6K with the old 1.4 8v engine, it might have done a small bit of good. Maybe the trouble with the 2008 1.4 16v engine is that it has no engine cover to quieten down the noise a bit, the injectors are also noisy. My oldest daughter has a late 2009 Ibiza 1.4 16v and yes it is a bit noisy, but it is a reliable and tough engine, she has owned that car from new and it gets serviced on time using correct parts, current mileage is 41K.
Edit:- my wife ran a 2003MY Polo 1.4 16v for 13 years from new - it had the engine cover type of air cleaner and it had sound proofing fitted to the bonnet.
