I'm not sure the panel filter will make that much difference as the airbox and ducting for the ST is massive (total length wise). This shouldn't have an effect on warranty (I've PM'd you with a full explanation).

I've just recieved my Pipercross induction kit for my ST and fitted it - Jesus what a difference!!!! The car is exactly the same below 3000rpm, then BANG, the whole characteristics of the engine change, aggresive, deep, powerful burbling sounds are given off as accelerate up the rev range, then, at 5000rpm the note changes from a burble to a scream and before you know it it time to change gear and enjoy it all again!!!
It works perfectly with the standard exhaust, which I think is one of the best manufacturer standard systems i've ever driven.
Thinking about lowering the car now, anybody got any ideas or suggestions?