Hi sportwagon dog,
It really depends on what sort of air filter you want? Do you just want to replace the old one with a standard one or do you want a performance on? You can pick up good air filters on ebay cheap, there are a lot of k&n ones which are good or if you are going the full hog then check this link out as this is what is going to be my next purchase BMC CARBON DYNAMIC ARIBOX | AIR FILTERS | AIR FILTER | car - bike - high performance - racing
these seem to be the real popular ones for these engines. They are a lot easier to clean the filter too or replace it. As you will find if the screws are rusty then you will find it hard to change the filter, I am in the process of changing mine due to the same problem. I tried to unscrew the bolts only to find that they started to snap so with the way they have put the air filter box you are going to have to get the box out from under the car, also you will need to disconnect the MAF sensor too. If you get one of these BMC Carbon filters they are so much easier to get to and clean. Also if you are thinking of remapping the car then i would suggest you cahnge the filter before you do anything like this. I have a jtd sportswagon too and love it but really hoping to mod it soon so keep watching. Any pics of yours??????