I have been through this with various N/A cars, the only real way to gain performance is to look at the air intake position and routing, some cars have restrictive designs from the factory..
2 things will make a difference
1) more air
2) cooler air
1 is achieved by making the route to the inlet manifold more direct and bigger, 2 is achieved by seating it lower down...once you have done this a freer flowing filter may help to free up some ponies..not to low though or you can hydrolock the engine in standing water.
however,paper filters are rarely the reason for poor induction, its normally the design of the intake as mentioned before, so it becomes about the induction sound, which can be nicer through some panel filters and the cost saving of buying a paper filter every 10k. You can damage the MAF (mass air flow sensor) with over oiling and it sounds to me as if you are a newbie to all of this so be careful! MAFs are not cheap and its one of the parts that is better replaced with OEM which = expensive...you MAY with all of this get 5bhp and a slightly crisper throttle response.
now onto the next bit..more air in means you need to get it out quicker for reals gains to be noticable, so the next step is a custom exhaust system and a re-map, I would also argue custom profiled fast road camshafts are high on the list of things to do.
all of this will gain you a maximum of 25 BHP for a cost of around £1000-1500...if you want an easily re-mapable car for not a lot of £££s buy a derv, with N/A petrols its always cheaper to buy a bigger engine from the outset.
diesels love a re-map!