Why would you need a K&N intake? Your car has a cold air intake already, and you won't notice any change in performance by changing.
A muffler changes the sound of the exhaust, it does absolutely nothing for performance. Seems like you're not very familiar at all with cars or what the parts do.
Swap the car to a V8. If already a V8, look into having the engine bored out, upgrading the pistons, etc and so forth. That will be the biggest bang for the buck. And STOP looking at cheapo parts, in hopes that you'll get anything good out of it.
