Well, I just got the K & N cone filter. Thought I was getting a Pipercross, but I gather they don't make one suitable. Anyway, the K & N took about 5 mins to install, and I haven't had much of a chance to try it out, but... it sounds great. Not like a roaring tiger, of course, but more of a tomcat than a kitten now...
It definitely feels more responsive. I only had to twitch the ankle and the car seemed to leap forward. Tomorrow, I'll test it on my weekly run to my parents' place (35km each way, uphill one way). The normal petrol consumption figure is 7.6L/100km, so it'll be interesting to compare.
Incidentally, my (very, very inexpert) eye noticed the airbox intake appeared to be coming from the front of the bonnet, over the radiator, rather than beneath the airbox somewhere as in the LS/LT set-ups I've seen pictured on here. There was also a small square of a spongy material in the bottom of the box. Would that be for the crankcase? Probably a dumb-**** question, I suppose...
Anyway, very pleased with my investment so far, although it's only early days...