hi Luke...mate ive had an airhammer CAI in a VE SS ute and now my sedan and cant go wrong..they get sent from Adelaide and its a simple installation...sounds great and I think you get a little more low down torque
Depends on your RTA (or SA counterpart) regulations. I know that VIC Roads don't allow oiled filters, which means K&N are a no-go. Lukey make a high-flow replacement filter that is non-oiled and it's around the same money.
Don't expect much from a different filter though. Mine has a K&N and noticed exactly FA difference. The filter will allow slightly more air through but the intake is almost as much of a restriction. My fuel consumption MAYBE dropped a little - but I'm not willing to confirm that, as it might have just been slightly more air in my tyres or something equally ineffective. The only tangible benefit is that you don't have to go buy new paper filters.
If you wanna keep it legal there will be a part number on the K&N filter google it and it should tell you what car it replaces then go to the manufacturer or auto shop and replace it as said on the above post i have not noticed any difference in fuel or performance in an oiled filter swapped to a paper filter.