I forked over $50 or so over the winter and plumbed a couple of K&N Air Filters on a few of our Exmark / Kohler CV-20 machines. WOW! In just the first two weeks I've noticed a huge difference. The machines seem to have a TON more horse power. They've also been really good on gas - about 30-40% better. I'm just curious to know if other people have gone this route and invested in these high performance filters and if so, what has been your experience?