at a guess nearly 10hp - the only reason why I know it is about this is that I went onto a roller dyno the other week and I thought at best my car would give me about 130 hp I ended up with 140hp just by removing the factory cardboard filter

on a hub dyno my car has about 163hp on a roller dyno you can expect to lose 20% hp because of power transfer so that would mean that I was only going to get the 130hp but ended up with 140hp