woah woah STOP!
1st thing to note is the plugs are absolutely fine... they are NGK BKR7E (1 grade colder than stock) which incidentally are not platinum (these aren't used in modded cars - manufacturers only use them for extended service intervals). Denso's are just a waste of money IMO - I've had no probs with NGK coppers on an engine putting out almost twice what it should do.
2nd thing to note is that AVA rollers are the fully braked type - IE to take a power reading they apply such a braking force on the rollers that the engine is under the most extreme load - the car sits there at wide open throttle and the wheels not spinning. This has two connotations - the first being the car produces more boost than it would on the road in the same way as driving up a very steep hill at WOT with 5 m8s in the car and a boot full of luggage would produce more boost than normal - more engine load = more boost. The 2nd being this abnormal engine loading and extra boost results in det that you wouldn't see under normal driving on the road. Many of the Scots on sxoc have been to AVA and the result is always the same - car runs 15psi on the road... goes on their rollers and produces 17 or 18psi, dets at the top end and AVA say lower boost... gets lowered to 15 or below on rollers... car goes back on the road and produces 13psi or less!
Hamish - I wouldn't worry too much m8, just keep an eye on the boost gauge when you mash the throttle and make sure you stick around 17psi or 18psi tops, back off if it tries to go above. Get yourself along to Dastek where they have a decent normal type rolling road that keeps the wheels spinning during a power run and also they have a wideband to check your fuelling with. Gerry there worked for Toyota Team Europe on the rally cars and knows his stuff.... he will advise you on fuelling / det throughout the rev range and hopefully set your mind at ease.
You don't need to buy a wideband lambda, you don't need new plugs - they're only a few hundred miles old lol.
HTH,
Bri.