There is only little gain to be made with just a panel filter. You may get a bit of a noise difference, but it will only be small.
The main problem with the polo's airbox is that it has a 5cm inlet. Then the next problem is that it has to find its way up and then take a sharp turn (90degrees) and find its way through a small hole against a flat wall.
I personally wouldnt bother changing the filter. If you are after more power the real answer is a new CAI, but this can be costy.
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