From what I understood is that platinum, double-platinum and the new iridium tipped plugs don't effect spark at all, they're just harder metals so over time there's less errosion of the plug tip meaning all those lazy people don't have to do as much maintenence on their cars, so based on what I've been tought, I'd say your friend was probably just driving on some bad plugs before and now he's getting the spark he should've been getting all along, but as far as the whole RPM thing goes, with a clutch, there should be no difference in RPM at a given speed in whatever gear it is he's using, a difference in power would only change how quickly the car reaches said RPM and speed. But at the same time it makes me think of how load effects speed and RPM, how at school on a dyno cars are capable of much higher wheel speeds than on the road due to the lack of wind resistance and engine load. Something else to think about I suppose.