what I would like to know is; would I get the same performance gain with just the K&N filter or would I have to buy the entire Injection kit to get some noticeable performance gain

 

Each option that you have suggested do have gains just not as much for the drop in filter compared to the FIPK (approx 26 HP - from K&N site) The FIPK comes with a smooth pipe and a cone filter which allows more air to flow in to the engine. If anything the sound that the FIPK makes while moving air through the system is really cool.

Have Fun & Keep on Truckin'
Dean