just replacement of your stock filter for a K&N will add a little(stress:little) HP, if you can use a different air cleaner base and can use a taller filter and an K&N x-treme air lid, it'll boost up your cfms and you'll gain more hp, but it won't work with the stock air cleaner base as the lid won't clear the carb and the cleaner"bolt "isn't long enough . All this will run at least a couple of hundred bucks for some hp and minimal mileage improvment.Cut out the back of the shaker and you'll get more air and a little more hp, but in my opinion, still not enough for all the $$ and time spent.