For the intake, go with the KKM. The K&N will not make any noticeable difference, do to the fact that air still has to travel into the restrictive airbox before it ever gets to the filter itself. The KKM however is an open air filter, which will not restrict air flowing to it. You should see a gain of 3-5 hp with the KKM. Low end torque may drop a tiny amount, but high end torque gain will compensate for the low end loss. Throttle response should improve slightly also. About your comment of others saying that exhaust mods should be made -- this is true, however it doesnt necessarily entail a lot of money. The least you should probably do is replace the OEM muffler with a performance one because the increased air flow through the new filter must be able to exit the exhaust quicker. Whats the gain of sucking more air in when you cant blow it out....nothing! Then of course if you wanted to, you could extend the exhaust mods later to a new y-pipe, resonator removal, or headers to let the exhaust flow even more freely (but that will cost a lot more than it sounds like you are willing to spend).
