LOL
Tolernces and clearances in an F1 engine are so fine, the engine is effectivly seized when its cold, F1 technology and a 1.8t that has done a fair few miles is such a big diffrence. Aso F1 cars run on race fuel and not stuff you get out the pumps, also the power they put out and the heat they generate is nothing on a roadcar even with stage 2. In a road car a spark plug is a spark plug, NGK are the same as OEM plugs, just OEM are branded VAG. Unless your playing about with a highly tuned engine, you arent going to benifit from iridum plugs.. FACT, so save your money and buy OEM plugs, if your running a mapped engine then of course some say try a heat range colder. Ive heard it all before im a mechanic i know this and that, so am i mate, but at the end of the day a plug is a plug, Why would anyone choose to use shitters over OEM plugs? There is a known issue with the Denso's and i think there aware of it, so if theres a known issue then dont use them.. simples.
Also what does a better flame mean? You using flame plugs now, i thought better plugs produced a better spark my self, which in turn ignites the fuel more effeicently? OEM plugs are fine for use on standard and mapped cars. If your running a hybrid turbo etc and your car is mapped with iridum plugs and decent fuel then your more likely to see a diffrence, in the real world it wont give you bhp or aceleration.