I wonder if anyone ever noticed how high their GD-3 VTEC 1,5L Matic engine could rev on 7 speed mode, prior to the auto upshift (that shall happen even when your finger don't touch the + button) ? When using the standar NGK plugs, mine never reached above 5900 prior to the auto upshift. But after I replaced them with VOLKER Iridium plugs, the engine was able to scream happily up to the red line (6300 RPM) before the auto mechanism took over the gear shifting..... does that result in more HP or higher topspeed ?