I reckon a replacement panel filter = not stock any more. Stock should mean no changes to engine whatsoever. Does that mean that a panel filter from Toyota Service and a panel filter from autobarn or supercheap auto as a replacement is a modification? A better definition is required, replacement of a "filter" to another "filter" is not deamed a modification by insurance companies, while extra tubing and CAI is. I would suggest that a normal-sized direct replacement panel filter, no matter the brand is a non-modifications. Obviously the insurance companies assume the same. ← Well, if you send it back to Toyota and get an OEM panel filter then of course its still considered stock. If something goes wrong with your engine, it will be covered under warranty. But if you get a K&N panel filter (or any other for that matter), then that has a possibility to void your warranty. K&N also advertises that their panel filters improve your car's performance. Anyway, I'm sure Lucio (or whoever is organising the prizes) will clear this up. ← Say What? A Direct Panel replacement filter such as a K&N voids warranty, what load a crock, not true as its fits inside the current housing, therefore it DOES NOT VOID WARRANTY and is classified as a consumable via Toyota. Been confirmed by a couple of service dealers that I rang today, also by insurance companies. If you replace the housing, such as the plastic bin that holds the stock size of the panel filter to something different structurally, it may void warranty. Therefore panel filters no matter make or model is NOT classified as a modification. ← Relax man, your car is stock as a rock. ← I agree, I really wouldn't consider a replacement filter alone a modification and in terms of increased performance we're probably talking a difference of 1kw. So Omn1potent goes into the stock box :D Also it's good that there's is a seperate category for 1zz's and 2zz's as we already which is the more powerful and we really want to be comparing apples with apples. Hope you can make it Danz, your's is the benchmark 1zz in VIC and I really want to compare mine to yours.