Can anyone tell me whether fitting a replacement air filter panel such as ITG, Green etc actually makes any difference to the power of a 02 WRX? I've read conflicting threads on Scoobynet and was wondering whether it is worth changing bearing in mind the oil on sensor malarkey

 

The good aftermarket filters do give better performance than the OE part, although the difference is probably more in terms of better throttle response than any easily quantifiable BHP gains.

As far as the oil on the MAF sensor problem is concerned, the New Age cars are supposed to have a more resilient element than the 99/00's, but if you want to be safe, just use the Green or K&N elemenets, which have hardly any oil on them.

 

Would you say panel is better than induction kit type?

 

It's a bit of a swings and roundabouts situation, with the theoretical benefits of the induction kit equalled or possibly even outweighed by the disadvantages.

Given that running an induction kit can cause a couple of weird problems, as well as invalidating your warranty, the panel filter is by far the easier option.