Personnelly ive got a K and N stg 1 filter and a DNA stg 2 filter. I bought the K and N first from my dealer, then found a second hand DNA stg 2 on ebay from another forum member on here.
For the differences in the K and N or the DNA im not sure, all the charts, graphs and information point towards the DNA being better, allowing more air flow into the engine and therefore giving you a better bang from your engine.
But for the differences between a stg 1 and 2 is massive. The stg1 really just gave me a bit more low down grunt and more noise, the stg 2 gave a huge increase in power low down and up in the rev range, also the snap while getting back on the throttle
